Historic, archived document

Do not assume content reflects current scientific knowledge, policies, or practices.

I

LAYOUTS AND OPERATING CRITERIA FOR AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

Marketing Research Report No. 891

U. 8. OEPl OF A^^eiSyiTUI^E

m:i 2 0 1971

CURBEflT SEP.IAL EEGOBOS

Agricultural Research Service United States Department of Agriculture

PREFACE

This is the last of a series of six reports submitted by P. H. Tracy under a research contract with the Transportation and Facilities Research Divi- sion, Agricultural Research Service, U.S. Department of Agriculture. These reports were prepared for Department publication by T. F. Webb, investi- gations leader, Handling and Facilities Research Branch, Transportation

and Facilities Research Division.

Contents

Page

Summary 1

Background of the study 1

Assumptions regarding plant operation 3

Suggested layout of the plant 4

Components of the facility 4

Arrangement of plant components 10

The plant site 11

Provision for plant expansion 12

How the plant operates 14

Receiving and processing milk 14

Making cheddar cheese 18

Preparing cultures 23

Handling whey 24

Cleaning equipment 26

Loading out 29

Labor requirements 30

Plant workers needed 30

Work schedules 30

Costs and possible benefits of labor-saving devices 36

Appendix: Refrigeration, heating, ventilating, and air conditioning 37

Refrigeration system 37

Heating system 40

Ventilating and air conditioning 41

Trade names are used in this publication solely to provide specific information. Mention of a trade name does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture or an endorsement by the Department over products not mentioned.

Washington, D.C. Issued April 1971

Fur sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 — Price 70 cents

ii

LAYOUTS AND OPERATING CRITERIA FOR AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

By P. H. Tracy ' SUMMARY

Automated and highly mechanized operating methods and an improved layout can reduce costs for dairy plants manufacturing cheddar cheese.

Labor costs in a plant handling 800,000 pounds of milk weekly would be about $136,500 less on an annual basis in an automated plant with an improved layout than in a nonauto- mated plant with a typical layout. Production for the automated plant is estimated to be 88 pounds of cheddar cheese per man-hour and for a nonautomated plant, 45 pounds. Costs of the additional equipment required to make these savings possible are estimated at $262,000. If 20 percent of this extra cost ($52,400) is al- lowed annually for costs of ownership and opera-

tion of the equipment, (depreciation, mainten- ance, insurance, taxes, and interest) the net savings due to automation would be $84,100 annually.

The cleaning operation has the greatest reduction in cost in the automated plant; how- ever, all operations can be performed more eco- nomically in the automated than in the nonauto- mated plant.

Layouts were developed for a plant handling 800,000 pounds of milk weekly. The layouts show arrangement of equipment and work and storage areas for the most efficient flow of prod- ucts, containers, and supplies throughout the plant. Provision is made for future expansion to double the original production.

BACKGROUND OF THE STUDY

The cheddar cheese industry had its begin- ning in the farm homes of the early American pioneer families. The first commercial plant was built in Rome, N.Y., in 1851. Wisconsin, however, soon became the leading State in pro- duction of cheddar cheese and by the mid-1960's produced over 40 percent of the Nation's output.

American cheese production, being to some extent an outlet for surplus milk, varies in

^ Dr. p. H. Tracy, formerly professor of dairy technology, Department of Food Science, University of Illinois, conducted the study and prepared the report under a research contract with the U.S. Department of Agriculture.

The author wishes to acknowledge the assistance of Wesley Wise of the Lake to Lake Cheese Co., Kiel, Wis., and T. H. Winkleman of Mojonnier Bros., Chicago, 111., in making this study.

quantity from year to year, but the general trend in production has been upward. The total production in 1964 was 1.2 billion pounds com- pared with 0.9 billion pounds in 1954. In 1930, 5 percent of the total milk production was used in making cheese. Thirty years later, this per- centage had increased to 10.9. During this time, the American people had definitely increased their use of this food. In 1930 the per capita con- sumption of American cheese was 3.2 pounds, and by 1960, this figure had increased to 5.4 pounds. The growing popularity of cheese is due to its relatively low cost, as well as the improved quality, packaging techniques, and marketing methods.

A definite part of the evolution of the cheese industry has been the growth in size of plants. This increase in size was made possible by im-

1

2

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

proved methods of producing and gathering milk from farms and mechanization and auto- mation of manufacturing. Traditionally, much hand labor has been required in making cheese, since for many years cheesemaking has involved methods based more on art than on science. Through research, many of the procedures have been improved and reduced to standardized ma- chine practices. Some tedious and extensive hand labor is still required in changing milk into Cheddar cheese, but mechanized and auto- mated methods are being developed at a rapid pace.

Modern cheddar cheesemaking involves care- ful bacteriological care of cultures; methods for controlling bacteriophage, a virus infection of starter cultures; automatic control of pasteuri- zation and cooling methods; use of large refrig- erated storage vats to hold over raw milk sup- plies to even out daily plant operation; large cheesemaking vats with mechanical agitators; mechanical methods for milling and salting the curd and for handling hoops; use of pallets and lift trucks; CIP (cleaned-in-place) cleaning of equipment; automatic control of steam produc- tion and refrigeration; and careful and detailed scheduling of workers in the cheese plant.

The heart of the process — cheddaring — re- mains a hand operation. Mechanized methods, however, are being developed. Cheddaring involves piling the curd down each side of the vat and cutting it into pieces about 5 by 4 by 26 inches, which are turned by hand to permit drainage of whey and to start surface sealing. After three or four turns, these long strips are cut into two crosswise chunks; and the front chunks are turned by hand and laid directly on top of the rear chunks. These pieces are then turned every 5 minutes and piled three or four high, the top pieces being transferred to the bottom with each turn. As the result of bacte- rial and rennet action, the curd begins to knit together and to become plasticized. This con- tinues until the curd is milled and salted. The knitting and plasticizing transform the curd from a mass of separate 14-inch chunks to a homogeneous mass that flows and flattens, be- comes somewhat rubbery, and has a final tex- ture very much like that of breast of chicken. It has a definite grain at this final stage before

milling, and continuous strips as long as 30 inches can be pulled from the mass.

If this turning procedure, which results in the flowing and flattening characteristic of the cheese, is omitted some savings in labor result, but the cheese has excessive mechanical holes and whey pockets. Such cheese is more likely to be curdy like open-textured Colby cheese.

Mechanization of this part of cheddar cheese- making, therefore, has not been used in this study, since it is not yet in general use in the industry. Several research workers in the United States and Australia at the time of this study have almost succeeded in duplicating with mechanical methods the true cheddar type, which is desirable for long-held cheese of the sharp-cured variety.

The purpose of this study is to supply the dairy industry with information and guide- lines that will be helpful in (a) increasing the productivity of labor in dairy plants, (b) im- proving quality by establishing more uniform and better controlled methods of operation, (c) improving working conditions by minimizing the number of jobs requiring difficult and tedi- ous labor, and (d) i-educing the amount of plant loss and shrinkage through more positive con- trol of operating procedures. Such information should be helpful in the remodeling of old plants as well as in building new ones.

New equipment that has been proved com- mercially feasible for mechanizing the proc- esses involved in the manufacture of cheddar cheese is described in the report, and the appli- cation of electronic control devices for auto- matic operation is explained.

A flow diagram and a layout of the site show- ing the desirable position of a cheddar cheese plant on an assumed location are provided for a plant handling 800,000 pounds of milk weekly.

The equipment needed to operate the plant is shown on the plant layout. The labor needed for performing the various operations involved is listed, and the labor cost for such an operation is compared with the estimated labor cost of a nonautomated and less mechanized operation of the same size.

Somewhat detailed explanations are given of the methods involved in operating a cheddar cheese factory, including disposition of the whey.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

3

ASSUMPTIONS REGARDING PLANT OPERATION

To illustrate principles of plant layout and methods of operation for an automated cheddar cheese plant, it was necessary to make certain assumptions. They were as follows:

1. The plant will handle 800,000 pounds of milk testing 3.6-percent fat and 8.8-percent milk solids-not-fat weekly. A 25-percent variation, plus or minus, in seasonal production will be al- lowed.

2. The milk will be purchased from local pro- ducers, and deliveries will be made daily in tank trucks.

3. The plant will operate 6 days per week. Workers will put in 40 hours per week.

4. The cheese will be made from pasteurized milk. Proper methods will be provided for the control and prevention of bacteriophage growth in the cultures and cheese vats.

5. The cheese will be made into the following styles and sizes:

Percentage Size Average Height of total of weight of

Style production cheese of cheese hoop

		Inches	Pounds	Inches
Twin	30	14 1/2 X 5%	30	91/2
Daisy	25	131/2 X 3%	20	6 1/2
Cheddar	25	141/2 X 11^^	75	151/2
10-lb. print	20	7 X 11 X 31/2	10	41/2
			(20-lb. hoop)

6. Provisions will be made for storing the cheese 30 days before shipment.

7. Equipment will be provided to condense the whey to 40-percent total solids for shipment to a dried whey plant.

8. Mechanical losses will not be considered.

9. The whey cream will be sold in bulk to a butter-processing plant.

An inventory schedule was developed from these assumptions. Since receipts will be 800,000 pounds per week, plus or minus 25 percent for seasonal variation, and since a 6-day cheesemak- ing week is desired, the plant will handle 180,000 pounds of milk for maximum production and 160,000 pounds for minimum (table 1).

The plant can operate with one day's receipts, or it can hold over all milk, or it can process part of it. Capacity of the holding tank is pro- vided for the maximum daily operation of 180,- 000 pounds (nine vats). With cold- wall storage

tanks, any amount of milk that cannot be put into the vats on schedule can be held to the next day.

Table 1. — Utilization of milk in a cheddar cheese plant handling 800,000 pounds weekly, with 25 percent allowance for seasonal in- crease in production

Quantity of milk — cheese

Day Received Stored Processed made ^

Pounds Pounds Pounds Pounds Monday . 142,857 105,715 180,000 (9 vats) 17,366 Tuesday 142,857 68,572 180,000 (9 vats) 17,366 Wednesday 142,857 51,429 160,000 (8 vats) 15,437 Thursday 142,857 34,286 160,000 (8 vats) 15,437 Friday 142,857 17,143 160,000 (8 vats) 15,437 Saturday 142,857 None 160,000 (8 vats) 15,437 Sunday 142,858 142,858 None None

1 Cheese yield based on formula: 2.68 X pounds of fat in given quantity of milk z= pounds of cheese produced.

As a practical measure, the daily production should be scheduled so that only one style is packaged from a vat. A breakdown on this basis would be:

3 vats, 30-pound twins per day 2 vats, 20-pound daisies per day 2 vats, 75-pound Cheddars per day 2 vats, 10-pound prints per day The schedule for one week is shown in table 2. The production of daisies and cheddars will need to be alternated every other Saturday to obtain the exact percentage specified for these two items.

Table 2. — Number of vats of each style of cheese made on specified day of week

Number of vats

Day Twins Daisies Cheddars Prints Total

Number Number Number Number Number

Monday	3	2	2	2	9
Tuesday	3	2	2	2	9
Wednesday	3	2	2	1	8
Thursday	2	2	2	2	8
Friday	2	2	2	2	8
Saturday .. .	2	2	3	1	8
Total	15	12	13	10	50

4

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

SUGGESTED LAYOUT OF THE PLANT

The suggested layout of the plant is shown in figure 1. The layout is arranged for efficient flow of products and containers, space utiliza- tion, equipment arrangement, labor utilization, and possible future expansion.

Two buildings are recommended. The building for the cheesemaking operations is rectangular. Its dimensions are 327 feet 6 inches long, and 184 feet 8 inches wide, covering an area of 60,479 square feet. Part of this area, which is adjacent to the milk-processing room, is not under cover. The milk storage tanks are on con- crete slabs and extend through the wall of the pasteurizing room.

Adjacent to this building is a second one con- taining 5,651 square feet of floorspace. The whey-processing facilities, the shop, the boiler room, and the refrigeration room are in this second building.

The two buildings are connected by an under- ground passageway, or tunnel, through which power, steam, water, whey, and refrigeration lines pass. This arrangement separates the whey-processing from the cheesemaking opera- tions. Since the whey evaporator uses large amounts of steam, the boiler should be located close by.

Components of the Facility

The major components of the plant are as follows:

1. Tanker-receiving shelter

2. Milk weighing, storing, clarifying, and pas- teurizing area

3. Cheesemaking area

4. Starter room

5. Hoop washing and storing and print-wrap- ping room

6. Cheese drying and paraffining room

7. Cheese storage room

8. Dry storage room

9. Loading dock

10. Refrigeration, shop, and boiler room

11. Offices

12. Plant locker and restrooms

13. Laboratory

14. Lunchroom

15. Whey-handling area

The components are arranged to provide for short, direct flow of products and containers and to minimize travel and handling. Requirements for space for each component are based on the size of the equipment and the working space needed for efficient operation. Size of storage rooms is determined by the number and size of items to be stored, the method of stacking, and the length of the storage period. Allowances for aisles are based on the type and amount of traffic handled. The components of the plant are designed and arranged so that expansion will not present a major construction problem.

Figure 1 shows the arrangement of each item of equipment in each component. Each item is numbered and is referred to by this number (in parentheses) in the discussion of the various components.

TANKER-RECEIVING SHELTER

As the amount of raw milk the plant will re- ceive from local producers will vary with the season, ranging from 85,714 to 142,857 pounds per day, the number of 3,000-gallon tank trucks delivering to the plant daily will vary from four to seven. After the milk is unloaded with the raw milk receiving pump (1), the truck tanks are washed. Other jobs performed in the shel- ter are inspecting the raw milk and taking sam- ples for analysis.

The tanker-receiving shelter provides space for two trucks at a time, so that one can be cleaned while the other is being unloaded. The shelter is 40 feet wide and 40 feet long. It has a 3-foot island 42 inches above ground level running lengthwise down the shelter dividing it into two truck positions. This platform is even with the walkway on the tank trucks to make it easy for workers to get to the tank manhole.

The floor of the tanker-receiving shelter should be constructed of brick tile pitched to- ward the rear at not less than one-half inch per foot to permit complete and rapid draining of milk from the tank trucks. A floor drain is lo- cated toward the rear of the receiving room to carry away the wash and rinse water used in cleaning the pump compartments on the tank truck.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

5

The truck tank washing assembly (118) is located in the shelter. It is mounted on a hoist and monorail to facilitate moving it into and out of the tank manhole and from one truck to an- other. A hose connects the cleaned-in-place (CIP) unit (80) with any tank having built-in spray-ball cleaning devices. Power-operated overhead doors permit the area to be closed off from the outside during inclement weather.

MILK WEIGHING, STORING, CLARIFYING, AND PASTEURIZING

Milk weighing. — After the raw milk has been inspected, it is pumped from tank trucks into one of the 3,000-gallon vertical weigh tanks (2, 3) and a sample of milk taken for laboratory analysis.

For automatic weighing of the contents of the tank, each tank should be mounted on three legs, equal distance from each other, and a load cell (weight-sensing device) attached to each leg. Each cell incorporates a deflector, and when the amount of milk in the tank changes, the de- flection is detected by an electrical differential transformer. The transformer produces an electrical impulse in exact proportion to the de- flection in the cell and transmits it to the re- ceiving control panel (85) where a direct read- ing in pounds of product is given. The accuracy of the load cells should be checked at regular intervals.

Milk storage tanks. — Three 8,000-gallon hori- zontal tanks (5,6,7) hold raw milk received from weigh tanks. They are equipped with level gages and are located side by side with the front heads extending through the processing room wall to the outside. This location not only elimi- nates the frequency of cleaning the exteriors of the tanks, since the bulk of the exterior extends outside the building, but also saves floorspace. The tanks are equipped with air-operated sani- tary outlet valves. They do not have sight and light fixtures as these fixtui'es are not needed on a gage-equipped tank that is cleaned in place. Each tank has 80 square feet of refrigerated surface for cooling or holding milk over from one day to another.

Since the milk will be received at about 3.6- percent butterfat content, standardizing clari- fiers or extra storage tanks for skim milk to be used for standardizing are not needed.

The raw milk storage tanks are equipped with indicating thermometers. Spray balls, welded into the interior, are connected to CIP hookup station (81).

In front of the raw milk storage tanks is a two-line sanitary header system. This system is used for all movement of product into and out of the storage tanks. One heade:" is used for re- ceiving milk from the weighing tanks or for transferring it from one 8,000-gallon tank to another, and the second to feed raw milk to the clarifier and the HTST (high-temperature, short-time) pasteurizing system. A 180-gallon per minute (g.p.m.) transfer pump (4) is used to transfer milk from one tank to another. Air- operated sanitary valves in the system, con- trolled manually or automatically from the con- trol panel (82), regulate the flow of milk. To al- low space for a two-line assembly and a pas- sageway, an aisle 6 feet wide should be pro- vided.

Clarifying and pasteurizing equipment. — Milk is clarified to remove extraneous mate- rial and leucocytes, then pasteurized, and fin- ally transferred through sanitary pipes to the cheese vats.

The clarifier (11) operates at the rate of 20,000 pounds per hour. Milk is pumped through the clarifier with a high-speed sani- tary centrifugal pump (10). From the clarifier it enters the HTST pasteurizing system through a balance tank (13). The balance tank is equipped with an air-operated float which modulates a throttling valve on the discharge of the pump (10). This valve controls the flow of milk through the clarifier so as to match the rate of the HTST flow. From the balance tank, the milk travels through the plate heat ex- changer (15) by a booster pump (14) and meas- ure flow-timing pump (16). The flow-diversion valve (18) directs the flow of milk after pas- teurization.

A water heating and circulating unit (19) provides the hot water needed to heat the milk in the heating section of the plate heat ex- changer. The equipment is arranged according to the product flow with adequate space for cleanup and passageway. Wash tanks (79) for manual cleaning of equipment are provided as well as an automatic cleaning setup ( 81 ) .

6

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

The measure flow positive pump (22) is used to pump the milk directly from the HTST unit into the cheese vat, where it is cooled in the cooling section of the HTST unit to 87° F., the cheese setting temperature. The HTST system is planned to process 20,000 pounds of milk per hour, but can be expanded by adding extra plates as needed. Recirculating water pump (119) is in this area also.

The dimensions of this area are 36 by 40 feet.

CHEESEMAKING AREA

Since the top daily receipts of approximately 180,000 pounds are for only a short period of the year, nine 20,000-pound cheese vats (29 through 37) 34 feet long and 51/) feet wide are proposed. The vats have round ends, are insulated and steam jacketed, and have overhead agitators of various speeds. They are spaced with whey- draining vats (41) and whey pump (43) as indicated on the layout. The cheese vat control panel (83) is located nearby. A tunnel under- lies the plant so that all utilities may be brought up from below to keep the cheesemaking room as free as possible of items that collect dust or are adversely affected by strong chlorine fog. The air-conditioning and filtering units (125) for the processing area are located here. Starter for setting the cheese is stored in a 300-gallon tank (20). The cheese utensil rack (120) and the two-compartment wash and sterilizing sink (121) are also located in this area.

The automatic curd milling, salting, and weighing machine (45) consists of the follow- ing parts:

1. A curd mill of the reciprocating cutter-box type; its speed can be regulated to suit the volume.

2. A hydraulically driven vibrator.

3. An elevating belt-type conveyor (44) .

4. A salt apportioning apparatus consisting of a weighing conveyor carried by a sensitive balance mechanism operated by electronic con- trols and a variable speed electric motor which drives a metering wheel in the outlet of the salt hopper.

5. A revolving mixing drum with an electri- cally operated discharge gate.

6. A hoop conveying assembly incorporating a pushrod-and-pawl type of conveyor and scales provided with a proximity switch.

The machine is L-shaped and occupies a space about 36 feet long in one direction and 12 feet long in the other. It is approximately 3 feet wide. Its height at the tallest point is 10 feet 11 inches.

Five stainless steel cheese presses (46) 34 feet long, each holding two rows of cheese, are provided. These presses are approximately 37 inches wide. The rated capacity of the presses is as follows:

Units

Cheddars 60

Twins 130

Daisies 178

20-pound prints 204

The pressure needed is obtained by double- acting sanitary hydraulic cylinders motivated by compressed air controlled by pressure-regu- lating valves.

A room 90 feet by 130 feet would house the milling, salting, and hoop-filling equipment, the cheese vats, the starter storage tank, and the cheese presses. Whey-separating and whey- cream-handling equipment are usually located in this room; however, recent information on bacteriophage control indicates that these items should be placed in the whey-condensing room along with the whey storage tanks.

STARTER ROOMS

The starter area is completely isolated from the rest of the plant as a precaution against contamination of cultures. It is located at the corner of the building adjacent to the laboratory and 40° F. storage room. Two doors open onto the enclosed dock. One provides access to the laboratory and the other to the powder storage room. An outside door is located at the end of the enclosed dock for the convenience of the starter.

The area is 30 feet wide and 40 feet long and is divided into a series of rooms. The entry room, a dressing room, a fogging room, and a storage room cover a combined area of 130 square feet. A vestibule and lavatory occupy 40 square feet. The vestibule has four doors — one to the fogging room, one to the lavatory, one to the mother culture room, and one to the bulk culture processing room. A room 20 ft. by 13 feet, divided in the middle, opens off the bulk culture room. It is used in part for storage of nonfat dry milk solids used for making culture,

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

7

and in part for mixing powder and water to make a 12-percent solution. The powder-mixing funnel and pump assembly (23) are located here.

The bulk starter processing room is approxi- mately 20 feet by 27 feet and contains two 300- gallon vacuum pressure stainless steel culture vats (24, 25) , leaving enough floorspace for two future vats (26, 27). The centrifugal culture transfer pump (28) is located between the two culture vats. A sink (129) is also in this room.

The mother culture room is 10 feet by 23 feet. It is equipped with autoclave, incubator, refrig- erator, laboratory desk, equipment for acidity tests, and the usual laboratory glassware needed for culture handling.

The entire area is air conditioned (123) to maintain a temperature of 70° F. The air is purified and is maintained at a pressure slightly higher than the outside so that any air leakage will be to the outside of the room.

The room is kept locked at all times; only the starter is permitted access.

HOOP- WASHING AND STORING AND PRINT-WRAPPING ROOM

This room is adjacent to the drying and par- affining rooms. A washer (49) for cleaning the hoops and a conveyor pan washer (48) are lo- cated here. The hoops come into this room on an overhead conveyor (50) and are placed on a dumping table (51). They then move on the stainless steel mesh-covered conveyor belt through the hoop washer, a stainless steel unit similar to a restaurant dishwasher. The first compartment contains a detergent solution which is a dilute nonfoaming organic acid. The temperature of this solution is automati- cally held at 160° F. The cleaning solution is sprayed onto the hoops from nozzles by a high velocity pump. In the second compartment, the hoops are sprayed with 145° water.

After the hoops are cleaned, some are stored until needed on stainless steel portable skids especially made for this purpose. The hoops that are needed immediately are returned to the cheesemaking room on the overhead conveyor (50).

A belt conveyor (52) in the room moves the cheese prints into the print-wrapping machine

(54) and the boxing machine (55). Round cheeses are moved by the conveyor (53) to the drying room.

CHEESE DRYING AND PARAFFINING ROOMS

The equipment in these rooms is used for dry- ing the various round cheeses after they have been dehooped in the hoop-washing and storage room. The cheese moves into the room on a belt conveyor and is placed in the box lids. These lids are then placed on portable shelves (56) con- structed of angle iron welded frames with five black iron painted shelves 52 inches long and 36 inches wide. The bottom shelf is 6 inches from the floor with 16 inches open space between shelves, making an overall height of about 75 inches. The shelves are moved with fork-lift trucks.

For the daisies and twins, removable shelves are placed between the permanent shelves at 8- inch spacings. This is not necessary for the Cheddars.

One portable shelf unit is needed for each of nine vats of cheese for 4 days, making a total of 36 units. This arrangement will provide a limited degree of flexibility. Cleaning is no par- ticular problem with the use of these shelves as an occasional hosing with hot water is sufficient.

Air-conditioning and filtering units (124, 131) are provided for the paraffining and dry- ing areas.

After the cheese is dried, the shelves, or racks, of cheese are moved by lift trucks to the paraffining room. The cheese must be coated with 235° F. paraffin to prevent loss of mois- ture and to protect the surface from mold growth. A paraffin tank (57) 24 inches wide, 24 inches deep, and 78 inches long, with an ex- haust hood (58) is provided for this purpose. This tank uses a power-driven mechanism for elevating the cheese and dipping it into the hot paraffin. The paraffin is heated by steam coils; its temperature is automatically controlled.

After paraffining, the cheese is moved to the table and scales (59) where it is boxed and weighed; it is then placed on pallets (60) on the racks and taken to the 40° F. storage room. The empty racks are returned to the drying room. Storage space is provided in the paraf- fining room for a reserve supply of pallets.

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

8

CHEESE STORAGE ROOM

Provision should be made for storing approxi- mately 30 days' production of cheese. Since nine vats of cheese will be made 2 days each week and eight vats 4 days, the total weekly produc- tion will be 50 vats. The 30 days' production will constitute 41/3 weeks or 216 vats, requiring 216 portable shelf units and pallets.

The pallets are 48 inches long and 43 inches wide. This width is used to permit loading two pallets side by side in a refrigerated semi- trailer.

To provide proper air circulation around the cheese, 5 feet of space is allowed for each row of pallets. The pallets are stacked two high in seven stacks, or 14 pallets in a row. To store 30- days' production, or 216 pallets, would require 15 rows and six pallets in the 16th row. The rows are 28 feet long, which leaves 12 feet for aisle space in front. In the center of the room, a strip 10 feet wide and 40 feet long is left vacant for aisle space. The total space i-equired is —

Square feet

16 rows of pallets, 28 feet long

and 5 feet wide 2,240

Aisle space in front, 12 feet by 120 feet . 1,440 Aisle space in center, 10 feet by 28 feet . 280

Total - - . 3,960

Total space provided in the plan is 4,400 square feet.

Double electric doors 7 feet high permit lift trucks to enter the room from the drying and paraffining room, and two such double doors open from the storage room to the enclosed dock. The room is also provided with eight cool- ing units (90) suspended from the ceiling.

DRY STORAGE ROOM

Much of the area in the dry storage room (1,600 square feet of floorspace) will be used for storing pallets of empty cheeseboxes, salt, wrap- ping supplies, washing powders and liquids, farm supplies, nonfat dry milk solids, and mis- cellaneous supplies, all delivered by truckloads.

Salt will be received in 30,000-pound lots. Bags of salt will be piled three to a tier and eight bags high, or 24 to a pallet. Counting the 13 pallets needed for a load, plus five pallets to be kept on hand as a safety margin, 18 pallets of salt will be stored in the room. Pallets are stacked two high.

16

Total square feet required : X 18 = 144.

Cheeseboxes

a. Cheddar boxes — 16-inch diameter X 14- inch height, nine to a tier, five high = 45 boxes per pallet. A truckload of 810 boxes requires 18 pallets. Ten-pallet reserve supply. Pallets stacked two high = 14 stacks. Total square feet required = 16 X 14 = 224.

b. Daisy boxes — 15-inch diameter X 51/2-inch height, nine to a tier, 13 high = 117 per pallet. Truckload of 2,340 boxes requires 20 pallets. Ten-pallet reserve supply. Pallets stacked two high = 15 stacks. Total square feet required = 16 X 15 = 240.

c. Twins use the same size of box as the Ched- dars. Total square feet required = 224.

d. 10-pound prints — This cheese requires an outer box in dry storage. One pallet will hold 1,600 outer boxes, 48 inches high. One month's needs plus 1 week's reserve. 1,080 boxes used per week = 5,400 boxes for 5 weeks. Four pal- lets will be needed, stacked two high. Total square feet required = 32.

Cleaners and sanitizers

These items are purchased in truckloads. One truckload would be :

32 drums general cleaner

12 drums sanitizer

28 drums acid Four drums per pallet = 18 pallets. Fourteen pallets reserve supply = 32 pallets. Pallets stacked two high = 16 stacks. Total square feet required = 16 X 16 = 256.

Farm supplies

Washing powder, liquid acid, spray, dairy cattle feed. Requires 2 pallets or 32 square feet.

Dried skim milk

Needed per week. Twelve 100-pound bags. Every other week delivery to maintain fresh- ness. Twelve bags reserve supply. Twelve bags per pallet. Three pallets with one stack two high. Total square feet required = 32.

Summary of floor space needed for dry stor- age room :

Square feet

Salt 144

Cheeseboxes:

Cheddars 224

Daisies 240

Twins 224

Prints 32

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

9

Cleaners, sanitizers 256

Farm supplies 32

Dried skim milk 32

Aisle space 416

Total .... 1,600

Certain items of equipment that need to be moved into or out of the plant can be taken through the storage room. If more convenient, hirge items can be taken through a removable panel (115) in the wall at the end of the tanker- receiving shelter. Doors, 7 feet wide, to the stor- age room are electrically operated. The room is provided with a unit heater (116) suspended from the ceiling.

LOADING DOCK

An enclosed loading dock 10 feet wide runs 110 feet across the front of the 40° F. cheese storage room. It is 54 inches above ground level. Electrically operated rollup doors directly op- posite the two load-out doors in the cooler will permit rapid loading of trucks with the cheese that is moved out each day. The hall ^long the dry storage room and hoop-washing room con- nects with the loading dock.

Shipping containers, salt, chemicals, and other supplies will be received at the door opening to the hallway.

BOILER ROOM, REFRIGERATION ROOM, AND SHOP

These rooms are located outside the main plant in the building that houses the whey-dis- posal equipment. One person per shift will op- erate all units housed in this building. An underground tunnel will carry water, power, steam, and refrigeration and whey lines to the tunnel of the main building.

Located in this area are the following items of equipment:

Boiler room — 35 feet by 33 feet

One 300-hp. boiler (86) One250-hp. boiler (87) Boiler feed water system (89) Incoming water-chlorinating unit (126) Hot water heating unit for sinks and water hoses (127)

Exhaust fans (130)

Removable equipment panel (115)

Refrigeration room — 35 feet by 60 feet One 25-ton ammonia compressor (99) Three 100-ton ammonia compressors (100,

101, 102)

Two 165-ton evaporative condensers (105, 106) (located outside building)

One 24-inch by 16-foot ammonia receiver (112)

One 113-ton sweetwater cooling unit (91) One 198-ton chilled water cooling unit (92) One 15-ton Freon condensing unit for the

cheese drying room (128)

Sweetwater pumps (93, 94, 94 A)

Chilled water pumps (95, 96, 97, 98)

Sump tank for evaporative condensers (108)

Evaporative condenser water spray pumps

(109, 110) One 10-hp. air compressor (113) Unit heater suspended from ceiling (116) Electric distribution panel (117)

Shop— 20 feet by 25 feet

The shop for repair of equipment is located adjacent to the refrigeration room. Work benches, repair tools, and mechanical supplies are located here. Exhaust fans (130) are located along the outside wall of the room.

OFFICES

The following offices are needed:

Superintendent's and engineer's office. — The plant superintendent and maintenance engineer share the same office because of the closeness of their work. It is located near the important proc- essing areas and contains 363 square feet. It is equipped with desks, chairs, correspondence files, and blueprint cabinet. One master station for the intercom system is located here for the necessary intraplant communication. Large glass areas are provided on one side for easy plant supervision. The office opens into a 195- square-foot hallway connecting the plant and an outside entrance.

Fieldman's office. — This office is adjacent to the superintendent's office and contains 154 square feet. It is connected by a hallway to both the superintendent's office and the laboratory.

General offices.- — Included in this general area are the offices (634 square feet), vault (97 square feet), women's lounge and restroom

10

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

(145 square feet), men's room (96 square feet), the viewing and reception area (871 square feet), and the manager's office (234 square feet) . The entire area is air conditioned ( 122 ) .

LABORATORY

The laboratory covers an area of 634 square feet and is located to the right of the main en- trance. It is air conditioned and the temperature is maintained at 72° F. The laboratory is di- vided into two sections, one for bacteriological control work and the other for chemical tests. The equipment needed to perform fat and acid- ity tests, sediment tests, moisture determina- tions, freezing point determinations, and whey solids tests are available in the chemical section. The bacteriological laboratory contains the glassware and media necessary to perform the standard procedures for qualitative and quanti- tative microbiological determinations, and tests for antibiotics and bacteriophage. An autoclave, flowing steam sterilizer, and microscope also are provided. Both laboratories have desks, tables, chairs, bookcases, filing cabinets, and cupboards for supplies.

PLANT LOCKER AND RESTROOMS

The plant's restroom for men workers is near the plant entrance. It is intended that only plant workers will use this room. Milk haulers and general service visitors will use the men's room adjacent to the lunchroom.

The 986-square foot area contains toilets, lavatories, clothes lockers, first aid facilities, and showers. Women plant workers will use the women's restroom adjacent to the lunchroom. This room is equipped with clothes lockers, first aid kit, chairs, a cot, and an air-condition- ing and filtering unit ( 124A) .

LUNCHROOM

The lunchroom, containing 385 square feet, is located to the right of the employee's entrance. Since most of the workers will bring their lunches, this room contains tables, chairs, and vending machines for dispensing milk, hot cof- fee, soft drinks, and candy bars. A rack for cur- rent trade magazines is provided. A bulletin board to carry announcements of general inter- est and importance to company employees will be mounted on one wall. The employees' time-

clock is located in the hallway at the entrance to the lunchroom.

WHEY-HANDLING AREA

The equipment for separating and condensing the whey is located in a separate building, which also houses the refrigeration and boiler rooms and shop.

One room, 36 feet by 42 feet, has alcoves for a 4,000 gallon vertical (silo) storage tank (63), a 16,000 gallon vertical (silo) storage tank (64), and two 6,000-gallon vertical (silo) storage tanks (75, 76). These silo tanks are actually lo- cated outside the building but are connected with the inside by alcoves. This room also con- tains two whey pumps, 20,000-pounds-per-hour (65, 65A), a 20,000-pounds-per-hour whey sepa- rator (67), a 20,000-pound-per-hour whey clari- fier (66), a 300-gallon whey cream cooling and storage tank (68), a 25-g.p.m. whey cream pump (70), a 20,000-pound-per-hour whey vapor heater (62), a 20,000-pound-per-hour whey double-effect recompression evaporator (72) equipped with a 3,000-pound-per-hour con- densed whey discharge pump and a cooling tower water return pump, a 20,000-pound-per- hour tubular preheater (71), a cooling tower (114) for the whey evaporator (located outside the building) , a 3,000-pound-per-hour con- densed whey cooler (74), a whey plate heat ex- changer (61), a 100-g.p.m. condensed whey pump (78) for loading bulk tank condensed whey hauling trucks, a three-tank CIP system (81A), and a whey process control panel (84).

A clarifier is included in this system to re- duce fat loss in separating whey cream.

A storeroom, approximately 15 by 25 feet, has a 5- by 8-foot men's room in one corner. The storeroom will be used for storing chemicals, janitor supplies, reserve items of equipment, sanitary valves, pipelines, and plumbing and electrical supplies.

Arrangement of Plant Components

In planning a cheddar cheese plant the vari- ous components should be arranged to provide for efficient processing and to minimize chances of bacteriophage contamination of starter or cheese curd. To accomplish this, the cheesemak- ing operations are located in the center of one

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

11

building with no outside doors or windows, the starter room is isolated at one corner of this building close to the cheese vats, and the whey- processing operations are in a separate building.

The arrangement of the processing areas pro- vides for the receiving, storage, and processing of milk to be carried out at one end of the build- ing; the cheese setting, cutting, cooking, ched- daring, milling, salting, and hooping in the cen- ter; and the cheese drying and paraffining between the cheesemaking room and the cheese storage room. This arrangement provides an uninterrupted flow of product from the milk- receiving room through the various processing steps, to stacking of the finished cheeses in the storage room.

Locating the laboratory and the offices of the superintendent, the plant engineer, and the head fieldman adjacent to the main offices brings the administrative personnel together. They can confer without the need of traffic through the plant yet have close contact with the processing operations in the plant.

Efficient flow of the product through the plant is further expedited by the use of a sin- gle-floor design and the use of pallets for the dry storage of supplies and the finished cheese. An overhead conveyor system permits the mechanical handling of the hooped cheese.

The lunchroom and locker room are conven- iently located for the workers entering and leaving the plant and for use during working hours. These rooms are sufficiently removed from the processing area to prevent a sanita- tion problem.

The various processing components of the plant are arranged to minimize the distance milk must travel as it passes through the cheesemaking process. This arrangement also provides for workers to change job assignments with minimum delay.

The compactness of the arrangement of the milk-receiving, storing, pasteurizing, and cool- ing equipment makes automation feasible with mimimum labor. The arrangement of the cheese vats in relation to the automatic milling ma- chine and the cheese presses and the use of an overhead conveyor make curd handling efficient.

The dry storage room is conveniently located for serving the cheese room with needed sup-

plies, such as salt, coloring (if used), wrapping materials, cleaning materials, and containers.

The cheeses leave the presses in hoops on con- veyors that pass directly to the hoop-washing and storage room, where they are transferred to conveyors that move them to the drying room. This system makes rapid handling of the cheeses and hoops possible with a minimum of labor.

The location of the paraffining room between the drying and the cheese storage rooms allows a straight-line movement of dried cheese through the paraffining treatment into the storage room without interfering with any other process being carried on simultaneously in the cheesemaking area.

Grouping the whey-processing operations, the repair shop, the boiler room, and the refrig- eration room in a separate building is desirable not only for sanitary reasons but also for mak- ing possible one-man supervision of all these operations. The various processing and CIP con- trol panels for the machines are located close to them, thus providing simplicity of control. Since the condensing operations need a large amount of steam and water, the vacuum pan should also be located here.

The plant incinerator is outside the rear door to the covered dock, convenient to both build- ings.

The Plant Site

The manufacture of cheese is usually concen- trated in the rural sections of the country where there are large numbers of dairy cattle but limited demand for milk for market milk and ice cream manufacture. Ordinarily, a site near a small town is chosen to insure the availability of the necessary supply of labor. Suitable power and an ample supply of good water are impor- tant. Unless city sewage is available, the soil must be suitable for the proper functioning of a disposal plant.

Locations near industries that produce objec- tionable odors or that attract rodents or flies should be avoided.

The type of both surface and subsoil will affect the cost of building. The most satisfac- tory base for low-cost foundation construction is either gravel or soft rockbed with enough grade to provide good drainage.

12

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

The land area should be large enough to pro- vide ample space for driveways, employee and visitor parking, and the handling of large trucks. Enough space should be available for simple landscaping in front of the building.

Figure 2 shows the suggested site for the Cheddar cheese plant. The area is 1,361 by 800 feet and comprises about 21/2 acres. A site of this size provides ample space for future expan- sion of the cheese operation and the possible addition of some other type of processing plant of agricultural products.

The site should be located on a main highway. Such a location is vital in the hauling of heavy truckloads of milk and supplies and the ship- ping of cheese. It is also desirable for adver- tising.

There is a 40-foot entrance to and exit from the area surrounding the plant. The entire area around the plant should be surfaced with con- crete or hardtop and sloped to drain. The area on the sides and rear of the site should be enclosed with a high steel-wire fence. A 120-foot clearance between the sides of the building and the edge of the plant area provides ample space for parking cars and maneuvering trucks. Ample room is also provided at the rear and in front of the building for trucks to pass. Space for a limited amount of landscaping in front is provided.

Provision for Plant Expansion

In planning means of handling a doubled plant capacity, lengthening the workday should be considered so as to get maximum use of the equipment. If this were done, present facilities, for the most part, would be ample, though some additional items would be needed.

Additional raw milk storage facilities would be needed. One 8,000-gallon storage tank would suffice, provided raw milk deliveries could be extended through the afternoon.

Another dry storage room and cold storage room would be needed. These facilities could be best located in an extension of the building, as shown on the layout. A 25-ton ammonia com- pressor (104) would be added to handle the cold storage room addition.

With the rapidly growing popularity of block cheese, all the additional cheese probably will

be put in 40-pound blocks. Thus a drying room would not be needed and the curd-handling operation would be simplified, resulting in in- creased production per man-hour.

Four more double-row cheese presses (47) and more pallets would be needed, and the starter room would need two additional 300- gallon culture vats (26, 27).

No additional equipment would be needed for the whey-handling unit since pickup of the whey cream and whey concentrate could be made twice as often, nor would additional oflSces be needed.

A less economical procedure would be to oper- ate with enough additional facilities to handle twice as much milk in approximately the same length of time. Again assuming that the added volume would be made into blocks, this would necessitate installing additional equipment or replacing present equipment with items of greater capacity or changing procedures as fol- lows :

1. Two 8,000-gallon raw milk storage tanks (8,9).

2. A 14,285-pound-per-hour cold milk clari- fier (12).

3. Three 20,000-pound-cheese vats and agita- tors, making a total of 12 (38, 39, 49) .

4. Three whey-draining tanks (42).

5. Four cheese presses (47).

6. A dry storage room.

7. A cold storage room.

8. Two 300-gallon starter vats (26,27).

9. A 300-gallon bulk starter storage tank (21).

10. By changing the cheese vat filling sched- ule from 1 hour to 35 minutes per vat and by increasing the capacity of the HTST unit by adding enough plates to handle 34,285 pounds per hour, the pasteurization needs would be pro- vided. The length of the holder tube (17) would be increased.

11. Adding a third eff"ect to the present 20,000-pound-per-hour whey evaporator (72) would increase the capacity to 31,000 pounds per hour (73), which is the rate the whey would be available.

12. Enlarging the plate cooler for the con- densed whey from its present capacity of 3,000

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

13

1361

•45 EMPLOYEE PARKING SPACES, 10' CENTERS

UNIMPROVED AREA

-«40^

■15 EXECUTIVE AND VISITOR PARKING SPACES, 10' CENTERS

-«40^-

FUTURE DRY STORAGE FUTURE 40°F STORAGE FUTURE HALL FUTURE BOILER ROOM

H I G H W

SCALE OF FEET 0 25 50 100

2. — A suggested layout for the site of an automated cheddar cheese plant handling 800,000 pounds of milk

weekly.

14 MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

pounds per hour to 4,600 pounds per hour by adding additional plates.

13. Replacing the present 20,000-pound-per- hour separator with a 40,000-pound-per-hour one, which would be operated at 30,000 pounds per hour.

14. A 300-gallon whey cream cooler and stor- age (silo) tank (69).

15. Adding another 6,000-gallon condensed whey storage (silo) tank (77), as the present two would lack 1,650 pounds capacity on 2 days a week during the peak season.

16. The raw whey plate heat exchanger would be adequate, as the maximum flow to the whey- processing area would not exceed 60,000 pounds per hour.

17. Additional pallets.

18. Increasing the vapor-line heater (62) to 31,000 pounds per hour.

19. Increasing the tubular preheater (71) to 31,000 pounds per hour.

20. A 300-hp. boiler (88).

21. A 25-ton ammonia compressor to handle the additional 40° F. cold storage room.

22. Additional cooling sections to the chilled water cooling unit (92).

23. An evaporative condenser spray pump (111).

24. A 100-ton ammonia compressor (103) and a 165-ton evaporative condenser (101 ) to handle the chilled water cooling unit. This is in excess of the size required, but the existing equipment should be matched so that standby capacity would be available.

HOW THE PLANT OPERATES

The major operating cycles involved in manu- facturing Cheddar cheese are (1) receiving and processing milk, (2) making the cheese, (3) preparing cultures, (4) handling whey, (5) cleaning equipment, and (6) loading out.

Receiving and Processing Milk

Raw milk is received at the plant in 3,000- gallon tank trucks and transferred to 3,000- gallon weighing tanks (2, 3) by a 180-g.p.m. raw milk receiving pump ( 1 ) . To perform this duty, the operator connects the receiving hose be- tween the tank truck outlet and the pump. The cover on the tank truck is opened. The weigh- ing tank into which the milk is to be pumped is selected on the "Fill" switch on the control panel (85), and the pushbutton actuated to aline the sanitary valves properly for the flow selected (fig. 3). This type of selector switch with a button actuator is used on several con- trol panels throughout the plant. Pushbutton 1 is pressed, which starts the pump transferring the milk to the weighing tank.

Pushbutton 1 is pulled out from the control panel approximately Vi inch to start and pushed in to stop. A pilot light located in the middle of the button, shows when the electrical circuit is operating. This type of pushbutton is on all the control panels, except where indicated.

When all the milk has been pumped into the

weighing tank, the weight is read by turning the "Tank Selector" to the tank just filled. The weight then appears on the indicator.

The tank trucks are washed by CIP proce- dures, using CIP unit (80) and spray assembly (118). The unit is mounted on a hoist and mon- orail to facilitate placing it into the tank truck as well as for moving it from one truck to an- other. All CIP features and controls are dis- cussed under "Cleaning Equipment."

Since milk is pumped out of the tank truck at the rate of 180 g.p.m., a 3,000-gallon tank truck can be unloaded in 17 minutes. The washing time, using CIP recirculation equipment, is 45 minutes. Allowing 20 minutes for sampling and for hooking up and disconnecting pipelines and CIP return pumps, the plant can handle a 3,000- gallon tank truck in 1 hour and 22 minutes. By overlapping the washing of one truck with the unloading of another, the plant can handle seven 3,000-gallon tank trucks easily in 6 hours (fig. 4).

After the milk is weighed, it is transferred into a storage tank and held until pasteurized by actuating the pushbuttons "Transfer From" and "Transfer To" in the control panel (82) (fig. 5). Raw milk transfer pump (4) is then actu- ated to transfer the milk into the 8,000-gallon storage tank selected. The pump will not start until the pushbuttons under the tank selector switches have been actuated. After the milk is

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

15

CIP UNIT 80

OFF FILL

.a

D D D m Is O D D

START STOP RESET

nnnannnnnnp

o

WEIGHT

3 •

TANK SELECTOR

CARD READER

o I

□

OPERATION PILOT LIGHT

Q PILOT LIGHT

PUSH BUTTON

Figure 3. — A suggested receiving and CIP control panel for an automated cheddar cheese plant handling 800,000

pounds of milk weekly.

transferred, the pump is stopped by button 4 or by moving a transfer switch to "Off," which breaks the pump circuit as well as the valve circuit.

The milk levels in the three 8,000-gallon stor- age tanks (5, 6, 7) may be read from the tank gages located on the left side of the control panel. The gages are air operated by a sanitary diaphragm in the tank wall near the bottom. A change in milk level is sensed by the diaphragm, amplified by compressed air, which results in a change in the liquid column within the gage. The gages are equipped with high- and low-level sensing devices which sound a horn at 7,500 and 250 gallons, respectively. The horn may be

stopped by pressing the "Horn Stop" button underneath the gages. When the high-level alarm sounds, a red light appears on the visual readout over the tank number. For low level, a green light appears in the visual readout.

The visual readout, located at the top of the control panel, informs the operator as to what his processing situation is at any moment with- out the necessity of studying all the various switches and gages on the panel. It also informs him which weighing tank (2 or 3) the receiving man is filling. The visual readout is connected to the selector switches electrically so that when a particular function is set up, an abbreviated indication lights up in the opaque glass over the

16

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

HOURS AFTER WORK BEGAN ON TRUCK NO.I

TRUCK NO.

I

2 3 4 5

6 7

37^k-45'— ^1 IHR. a 22 MIN.

2 HR. a 7 MIN.

PREPARATI0N-20MIN./ PUMP OUT -17 MIN

IDLE

WASH- 45 MIN.

2HR. a 52 MIN.

3 HR. a 37 MIN.

I

4 HR. a 22 M

N.

5HR. a 9MIN.

5HR. a 54 MIN.

Figure 4. — A time schedule for receiving milk and washing tank trucks in a cheddar cheese plant handling 800,000

pounds of milk weekly.

equipment number. Examples of this would be the words "Fill" over (2), "HTST Feed" over (6), "Vat 31" over (15), "Tank 5" over (81) and, "Clean" over (5) . Under this condition, the following processes would be taking place :

The receiving man is pumping into weigh tank (2).

The HTST system is using milk from 8,000- gallon tank (6).

The HTST system is discharging into cheese vat (31).

The CIP unit is cleaning 8,000-gallon tank (5).

The 8,000-gallon tank (7) and the 3,000-gal- lon weighing tank (3) are idle.

The flow of milk and cheese from receiving through filling are shown in figure 6.

Clarification and pasteurization of the milk are performed next. The storage tank which will supply the first milk used is selected on the "HTST Feed" selector switch. The centrif- ugal pump which feeds the clarifier (11) is

actuated until milk appears in the balance tank (13) and is then shut off. This fills the clari- fier with milk, which will lubricate the seals while it is being brought up to speed, at which time clarification and pasteurization may begin.

The cheese vat that is to receive the first milk is selected on either of the "HTST Dis- charge" switches. These two switches are inter- locked so that if one switch is already set on a cheese vat the other will not function until the first switch is set on "Off." The HTST system is started by:

1. Starting heat and circulating unit (19) and cooling water circulating pump (119).

2. Turning on steam and cooling water sup- ply valves.

3. Setting HTST (15) recorder-controller on proper pasteurizing temperature (161.5° F.).

4. Setting HTST cooling section recorder- controller on proper cheese setting temperature (87° F.).

5. Setting the "Totalizer" for pump (16) on 20,000 pounds.

HTST RECORDER CONTROLLER 15 / ^

HTST COOLING SECTION RECORDER CONTROLLER

TRANSFER

\fo/

REFRIGERATION

© ® © ® 3 ©©©(§} ii>

AGITATORS © (5 @ izjl

FlGURB s„gg„sle.l process control panel for .n auto.naled Cheddar cheese plant handling 800,000 pounds

of milk weekly.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

17

18

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

6. Starting clarifier feed pump (10) and measure flow pump (16) .

The milk will then flow through the clarifier (11) to the balance tank (13). An air-actuated throttling valve on the discharge of the pump (10) controls the flow through the clarifier to the rate required by the HTST pasteurizing system. The measure flow pump (16) will pull the milk through the raw milk side of the regenerator and push it through the remainder of the pasteurizing system to the cheese vat. The milk will be diverted for a moment back to the balance tank (which serves to reintroduce sublegal temperature milk into the system) by flow-diversion valve (18) until the 161.5° F. temperature is reached. When this temperature is reached, the flow-diversion valve changes position causing the milk to flow thvough the pasteurized side of the regenerating section, the 16-second holding tube, the cooling section, and on to the cheese vats.

The booster pump (14) comes on automat- ically when the flow-diversion valve .goes into forward flow, as the pump is interlocked electri- cally with the recorder-controller. In addition, a pressure switch in the system prevents the pump from operating if the pasteurized milk pressure in the regenerating section is less than the raw milk pressure. This makes certain that should any leakage in the regenerating section occur, it will be toward the raw milk side.

The instruments located in control panel (82) automatically control the pasteurization tem- perature and final temperature of milk going to the vats. These temperatures are recorded for use by health regulatory agencies as well as management. After operating a few minutes, the temperatures will equalize at the following:

"F.

Raw milk in 38.0

Raw milk out of regenerator 109.5

Raw milk out of heater 161.5

Pasteurized milk out of regenerator 90.0

Pasteurized milk out of cooler 87.0

A holder tube (17) is used in the HTST sys- tem to hold the milk for 16 seconds at 161. 5°F. to insure proper pasteurization. Higher tem- peratures should not be used because of their detrimental eflfect on the yields of cheese.

When the flow-diversion valve (18) is changed to forward flow, the "Totalizer" for the measure-flow pump (16) automatically begins

to tabulate the amount of milk passing through the system. This instrument tabulates the vol- ume passing through the pump. The measure- flow pump is actually two positive displacement pumps in series, one pump head providing the pressure and the second operating at no pres- sure drop. Thus, the revolutions traveled by the second pump head are very closely propor- tioned to the volume of milk passing through the pump. These revolutions are calibrated in pounds on the totalizer.

When 19,000 pounds have passed though the measure-flow pump (16), the totalizer horn sounds, indicating to the operator that in 3 min- utes 20,000 pounds of milk will be in the cheese vat. At that time, the operator pushes the "Manual Divert" button, which will momentar- ily cause flow-diversion valve (18) to divert the milk back to the balance tank (13). While hold- ing the manual-divert valve in, the operator advances the "HTST Discharge" switch to the next vat and, then, releases the manual-divert valve. The milk will then flow into the next cheese vat. The totalizer for pump (16) is reset to "0" and the next vat is filled.

The totalizer horn may be turned off by pushing "Horn Stop."

If the operator fails to depress the manual- divert valve when changing from one cheese vat to another, the milk will pass through a relief valve back to the balance tank. This is not re- commended, however, because it creates exces- sive pressure on the plate heat exchanger ( 15 ) . It is used only as a safety device.

Making Cheddar Cheese

Starter, a bacterial culture chosen for its Cheddar cheesemaking qualities, is stored in a 300-gallon vacuum pressure tank (20). It is forced into the pasteurized milk line leading to the cheese vats at the time the vat is starting to fill by the measure-flow pump (22). The operator sets the desired quantity of starter (1.00 to 1.25 percent, or 200 to 250 pounds) on the totalizer, and the pump is started by pushing button (22). When the correct amount of starter has been added, the pump shuts off automatically and the totalizer is reset to "0" for the next vat. The outlet valve on the starter tank is controlled by the "Starter" selector

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

19

switch. Opening and closing tliis valve for each addition is not necessary because the measure- flow pump (22) prevents backflow.

Other features of the control panel (82) in- clude pushbuttons for the tank agitators and for the cold-wall sections on the 8,000-gallon storage tanks (5, 6, 7). These pushbuttons are connected to solenoid valves which admit refrig- erant to the cooling sections of the cold-wall tanks.

A strip chart recording thermometer could be used to maintain a 24-hour record of the tem- peratures of raw milk in the weighing tanks (2, 3) and the storage tanks (5, 6, 7); however, its expense does not seem warranted for a plant of this type, receiving all milk in bulk. Therefore, indicating thermometers are used.

When the first 20,000-pound cheese vat (29) is filled, the cheesemaker adds 60 ounces of rennet, an enzyme, diluted with 10 gallons of

cold chlorinated tapwater. This is repeated on subsequent vats (30 through 38) when they are filled. To mix in the rennet, the mechanical agitators are operated the length of the vat three times by turning the agitator start switch on the control panel (83) to "Automatic" (fig. 7.).

The agitator automatically stops after it has traveled the length of the vat three times. As the agitator reaches the end of a vat, it strikes a limit switch which is connected to a stepping- type relay. At the third engagement, the step- ping relay will turn the agitator off". Shortly after the rennet is mixed in, the agitator pad- dles are removed.

CUTTING THE CURD

The proper time for cutting the curd varies from 20 to 25 minutes after adding rennet; it is determined by inserting a spatula into the

2'- 6"

I

TEMPERATURE CONTROLLER

50^	-

AUTO OFRmANUAL

AGITATOR

0

□ □

STOP STOP

0 0

sfgRT START

o o

lEAT HEAT HI LO

Q

PILOT LIGHT

PUSH BUTTON

Figure 7.— A suggested cheese vat control panel for an automated cheddar cheese plant handling 800,000 pounds

of milk weekly.

20

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

coagulum at a 45-degree angle and raising it slightly to judge firmness of the curd. Cutting the curd at the right time is essential. If it is cut too soon, excessive fat and curd loss occurs. If cut too late, the curd particles will be irregular, resulting in nonuniform whey expulsion. When the cheesemaker decides the curd is ready, it is cut immediately with curd knives.

A curd knife is a rectangular shaped metal frame with stainless steel piano wires stretched vertically or horizontally. The wire spacing is set to secure the desired size of curd particle (1/4 inch). In cutting the curd, two men cut the length of the vat, one using the horizontal knife and the other the vertical knife, drawing them through the coagulum, side by side. After cut- ting the length of the vat, the knives are re- versed to opposite sides of the vat and a return cut the length of the vat is made, finishing a horizontal and vertical cut on each side of the vat. To finish cutting, the curd is cut across the vat with the vertical knife.

Twenty minutes after the curd is cut, whey begins to move from the particles. The slight firmness that has developed permits slow ag- itation of the curd in the whey. Mechanical pad- dles are inserted into the agitator shaft, and the agitator switch is turned to "Manual" on the control panel (83) to start agitation. Steam is turned into the vat jacket by pressing the "Heat Lo" button. This admits steam from a line, which will raise the temperature of the contents of the vat 2° F. in 5 minutes. The tempera- ture-controller in the control panel (83) is set for 100° to 104°. The temperature to which the curd is heated will determine the amount of moisture retained in the cheese. At the higher temperature, the moisture content of the cheese will be lower. The moisture content will vary from 35 to 38.5 percent. (The legal maximum is 39 percent.) When the desired temperature is set on the temperature-controller, the steam in- put will be modulated to maintain that tempera- ture until the steam is turned off" by push- button.

MAKING ACIDITY TESTS

Sixty minutes after the curd is cut, a sample of the whey is gathered in a stainless steel cup. From this sample, 9 milliliters (ml.) are pipetted and tested for acidity. The acidity

should be between 0.13 and 0.15 percent. Half the whey is then drawn by gravity into the whey-draining tanks located at the outlet valve of each vat. The tanks are 16 inches in diameter and contain an additional strainer. They are of such height that the level of whey is no higher than the level of liquid in the vat, thus prevent- ing overflow during drainage. A positive-dis- placement pump (43) forces the whey into one of the whey storage tanks.

After half the whey is drained from the curd, the vat strainer is removed and the curd is again agitated for 5 minutes at medium speed. The paddles are then removed; the whey strainer is replaced; and the vat valve is opened. The curd is then pushed with the stainless steel curd rake toward the rear and sides of the vat, forming a trough lengthwise of the vat to facil- itate drainage of the whey. The trough should be about 8 inches wide and the curd 4 to 5 inches deep.

A sample of the whey is again taken in a stainless steel cup from the bottom of the vat. A sample of the whey is removed from the cup with a 9-ml. pipette and tested for acidity. This test is made on a stainless steel table in the vat area. At this point, the acidity of the whey should be 0.20 to 0.25 percent. As the whey continues to be expelled from the curd, it accu- mulates in the whey-draining tank.

THE CHEDDARING PROCESS

The curd is next cut into slabs 18 inches long and 2 inches wide by hand with a cheese knife, the curd being cut from the center of the vat to the sides to produce blocks about 5 inches wide, 4 inches thick, and 26 inches long. Starting at the rear and moving forward, each block is turned on its side with sufficient space between blocks to permit drainage. If the whey does not drain sufficiently from the curd, a sour flavor will be noticeable in the finished cheese. This sour flavor will continue to develop and will re- sult in an off-grade cheese. The block-turning process is repeated until each block has been given a quarter turn four times.

The row of blocks is next cut through the cen- ter lengthwise; the cheesemaker then turns each alternate cut block over and places it on top of the one next to it. The blocks are again turned, placing the top block on the bottom

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

21

of the vat without turning and then flipping the bottom piece end for end and placing it on top. This somewhat tedious process is necessary to prevent uneven evaporation from the curd, since uneven drying will result in nonuniform acidity development and a variation in color, both of which will cause streaks in the cheese.

The next step is to arrange the slabs in tiers three high, placing the top piece on the vat bot- tom and flipping the other two end for end. Each time, one end of each block is in contact with the vat wall as an aid in retarding evapora- tion. The three-high stacking is done twice, after which the blocks are stacked four high, using the same precautions to avoid surface drying of the curd.

At this point approximately 1 hour has elapsed since cutting the curd into the 5- by 4- by 26-inch slabs. The four-high tiers are turned twice at 10-minute intervals, after which the whey is again checked for acidity, which at this stage should be 0.50 to 0.60 percent. If the acid- ity has not reached 0.50 percent, the blocks are restacked until the proper acidity has developed.

The curd particles are now matted together and are somewhat plastic. This change, known as the cheddaring process, is necessary to obtain the proper flavor and body in the finished cheese.

Automation of the cheddaring process has been tried, but at the time of this study no proc- ess has been developed that has proved en- tirely successful on a commercial basis. When a satisfactory method has been perfected, savings in labor will be considerable.

MILLING, SALTING, AND HOOP FILLING

The curd blocks at this point measure approx- imately 30 by 12 by 2 to 3 inches. They are next placed on 14-inch conveyors (44) located in every other row between the cheese vats. These conveyors move from left to right to another belt conveyor moving at right angles, which picks up the curd blocks and delivers them to the curd milling, salting, and weighing machine (45). These conveyors are equipped with stain- less steel belts that are easily cleaned and sanitized.

The cheddared curd is fed into the hopper of the curd mill, and the milled curd falls onto the

tray of a vibrator which spreads it evenly on the elevating conveyor. From the top of this conveyor, the curd falls onto the belt of the weighing conveyor. The weight of the curd is translated by the balance mechanism and the electronic controls into a corresponding speed of rotation of the salt-metering wheel and thence into an automatic delivery of a predeter- mined amount of salt proportional to the weight of the curd. Usually salt is added at the rate of 4 pounds for each 1,000 pounds of milk proc- essed.

The curd and the salt are fed simultaneously into the mixing drum where they are thor- oughly mixed. The salted curd is then dis- charged from the drum into the hoop and dressed with single-service bandages on the scales of the hoop conveying assembly. When the hoop has received the required quantity of curd, a switch in the scale causes the discharge gate to close. After a preset short delay, the pushrod-and-pawl conveyor automatically moves the filled hoop away, brings an empty hoop onto the scales, and the filling cycle is repeated.

An overhead conveyor system (50) brings the washed and sanitized hoops from the hoop storage room to the milling and salting ma- chine, where single-service press cloths are inserted before the curd is added. The same con- veyor takes the filled hoops to the cheese presses.

CURD PRESSING

The hoops of curd are placed end to end in one of the four 34-foot double-row cheese presses (46) which are located near the milling and salt- ing machine and parallel to the cheese vats. To permit the added salt to dissolve completely, the hoops remain here under no pressure for a half hour, after which 50-pound gage air pressure is applied for a half hour. Pressure is then re- leased ; the hoops are removed ; and the single- service bandages are redressed. The cheese is put back into the hoops and returned to the press, where it remains under 50-pound gage air pressure overnight. The next morning, the hoops of cheese are removed from the press and placed on overhead conveyors (50) which take them to the hoop-washing and storage room.

22

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

HOOP WASHING AND STORAGE

When the stainless steel conveyor carrying the hoops of cheese reaches the hoop-washing and storage room, it dips down to table height. The hoop is then lifted from the conveyor pan, inverted at the dumping table (51), and the cheese removed. The empty hoop is placed on a conveyor belt which takes it into and through the hoop washer (49).

After the twin, daisy, and cheddar cheeses are removed from the hoops, they are placed on a conveyor and taken into the drying room. They are placed on the portable drying shelves and moved by pallet truck to an assigned area of the drying room.

The print cheese is moved on the belt con- veyor (52) from the dumping table through the print- wrapping machine (54) to the boxing table (55).

At times some of the washed hoops will be placed back on the overhead conveyor to be reused. At other times, all of them will be stored on pallets in this area until needed. For nine vats of cheese, nine pallets of hoops of the type needed to match the styles of twins, daisies, Cheddars, or prints being made are re- quired. Hoops should not be stored nested but stacked so that air can circulate around them to permit drying.

The overhead conveyor pans travel through a washer after the filled hoops are removed from the conveyor and before the cleaned empty hoop is placed back on the conveyor. The washer sprays the hanging arm and pan with the same kind of acid solution that is used in the hoop washer. This is followed by a warm water rinse at 145° F. The pans are automatically tilted for a distance of 10 feet to allow all rinse water to drain, since the pans have solid bottoms to prevent salty whey from dripping to the plant floor while the hoops are being conveyed from the hoop filler to the cheese presses.

DRYING AND PARAFFINING THE CHEESE

The round types of cheeses are placed on

portable shelves (56) and dried for 48 hours at

55° F. and 70 percent humidity. After drying,

pallets of cheese are taken to the paraffining

room.

The paraffin tank (57) has a power drive for the cheese elevator, which will dip five Ched- dars, 14 daisies, or 10 twins into the paraffin; there is an automatic shutoff on the upstroke. An overhead hood (58) carries away the vapors.

PACKAGING THE CHEESE

After paraffining, the cheeses are weighed and boxed, with the weight and vat number marked on the box. These boxes are then placed on pallets (43 by 48 inches), all the cheese from one vat (1,930 pounds) being kept on one pallet. One box from each vat is set aside for later in- spection. This box is stored in the same room with the pallet of cheese.

After the press cloths are removed, the prints are wrapped with a laminated multilayer of foil and plastic material. A heated press (54) seals the print wrapper to the cheese. All six surfaces of the press are heated by 170° F. oil circulated through the hollow plates of the sealer. The cheese is pressed for 17 seconds to seal the wrapper.

CURING

The wrapped prints and the boxed paraffined round cheese are moved by pallets into the cheese curing room (40° F. storage room) by electrically powered forklift trucks. The cheese is left in the curing room for 30 days before being shipped to the market.

LABORATORY TESTS IN CHEESEMAKING

Samples of producers' milk are tested periodi- cally in the laboratory for fat, bacteriophage, antibiotics, sediment, and possible watering. Periodic checks are also made on the sanitary quality of plant tapwater. A sample of cheese from each vat is checked for fat and moisture content when manufacture is completed. The cheese is held 30 days and then checked again for fat and moisture content before being shipped. At this time, the cheese is graded for flavor, color, body, and texture. Phosphatase tests are made of the milk from each vat set for cheese. An acidity test is made hourly of the whey before and after condensing, and the con- densed whey is checked for total solids. Two men will be needed to perform these tests.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

23

Preparing Cultures

The starter (culture) maker begins his work- day by changing into clean white clothing and clean rubber boots in his dressing room. Before entering the working area, he passes through the chlorine-fogged room. He will then sample the bulk starter set the previous day for flavor, odor, and acidity. If the acidity reading is in the range of 0.9 to 1.1 percent (starter is made from 12-percent solids skim milk), the worker will cool the bulk starter from 70° to 40° F. with sweet water.

The intermediate culture set the previous day is also sampled for flavor, odor, and acidity. If it is in the same acidity range as that of the bulk starter, the intermediate culture is cooled in the water bath to 40° F. The flask of interme- diate culture used for these tests is discarded and not used for bulk inoculation.

For bulk culture, two 300-gallon starter vacu- um pressure processors (24, 25) are used. Usu- ally 1 percent of bulk culture will be needed, but this percentage may vary with changing culture activity and changing amounts needed in the milk in different seasons. One-percent inocula- tion on a peak day of 180,000 pounds would re- quire 1,800 pounds of bulk culture. Two 300- gallon units have been chosen to permit making the starter one day, testing the following day, and using the third day. If a starter is found defective in one vat, the batch is discarded and another immediately set up for testing the fol- lowing day. This procedure lessens the chance of ruining a day's make of cheese.

About 4 p.m., the operator will have drained the starter storage vat (20) which was filled with culture made 2 days before and will have pumped it into the cheese vats. He will then clean and sanitize the vat, and refill it from the batch he has checked.^ He will rinse the empty starter processor (24 or 25) with cold water and then clean it with a detergent, following with an

^ To check the activity of the culture, 9.5 ml. of pasteurized milk is transferred into a sterile bottle. The milk is tempered to 90° F. and 5 ml. of test culture is added and mixed with the milk. The sample is incubated at 90° for 4 hours, after which the titratable acidity is determined. A lactic acid value of 0.6 to 0.7 percent rep- resents a very active culture; 0.5 to 0.6 percent is an average culture activity; less than 0.5 percent is a slow culture that should be discarded.

acid wash and rinse. Finally, the starter proces- sor will be steam sterilized at 20 pounds pres- sure for 1 hour.

Immediately after the equipment is sanitized, the starter maker will pump mixed water and nonfat dry milk into the starter processor in such proportions as to make a 12-percent solu- tion. The nonfat dry milk used is low-heat Grade A tested powder especially made for making starter. Water and powder are recombined in a mixing funnel (23). As soon as the required pounds of reconstituted mixture are added, the solution is heated with steam in the processor to 190° F. and maintained at that temperature for 1 hour.

During the 1-hour holding period, the starter maker makes a 12-percent mixture of nonfat dry milk and water in a sterile 5-gallon stainless steel can, using a sterile stirring rod. This is divided between the required number of flasks for intermediate culture plus one for sampling. The flasks are heated in an autoclave at 10 pounds pressure, equivalent to 240° F., for 1 hour. Temperature in the autoclave is then brought down gradually, and the flasks are re- moved to a water bath where they are tempered to 70°.

Floors of the dressing room, mother culture room, powder mixing room, and bulk culture room are all thoroughly scrubbed and rinsed daily. Just before the starter maker leaves for the day, the rooms are fogged with 500 parts per million (p. p.m.) of chlorine. Then the interme- diate culture is inoculated with a fresh sample of commercial freeze-dried culture from a batch of culture that has been pretested for activity and reliability for cheddar cheesemaking. Inter- mediate culture is then carefully agitated and set in the 70° F. incubator.

Then the starter maker removes the flasks of intermediate culture that were set the previous day and adds the required amount of intermedi- ate culture to the bulk starter processor (24 or 25) containing pasteurized reconstituted nonfat dry milk. The mixture is agitated 5 minutes with the power agitator, temperature is checked to insure setting at 70° F., and the air-condition- ing thermostat is checked to make sure the room temperature is 70°. The starter maker locks the door of the starter room when he leaves.

24

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

Handling Whey

Whey, a prime source of bacteriophage, is handled in a separate building. Workers in this building are not premitted to enter the operat- ing areas of the cheese plant. The outside doors to the working areas of the cheese plant are kept locked at all times.

The whey that drains from the curd collects in the whey draining tanks (41) located near the outlet valve of each cheese vat. This whey con- tains about 0.25- to 0.35-percent fat and 6.5- to 7.0-percent total solids. Since these solids have enough food value to justify their salvage, pro- visions are made to separate the fat for cream to be used in buttermaking and to condense the remainder of the solids for making dried whey, which can be used for either human or animal food. This method of whey disposition avoids the problem of stream pollution and the expense of setting up and operating a waste disposal system at the plant.

Since whey is a prime source of bacteriophage, it should be handled in a remote locati6n. There- fore, a pump (43) is provided to move the whey through a 21/2-inch sanitary pipeline located in the tunnel beneath the building to the whey- handling plant. Since the rate at which whey is drained from the vats varies, a 4,000-gallon ver- tical storage tank (63) is used as a surge tank to even out the flow through the whey separat- ing and concentrating process.

Warm whey is cooled to 40° F. to prevent buildup of acidity while in storage. A centrifu- gal pump (65) passes the whey through a plate heat exchanger (61) which cools the whey first with city water and finally with 34° sweet water recirculated from the sweetwater cooler (91) by pump (94) . The whey then passes into a 16,000-gallon vertical storage tank to await further processing.

The air-operated inlet-outlet valves for the 4,000-gallon and 16,000-gallon storage tanks, as well as the pumps, may be controlled from con- trol panel (84) (fig. 8).

To start the separating and evaporating proc- ess, the bypass control for the 20,000-pound- per-hour double-eff'ect recompression evapora- tor (72) is turned to "On" position. This closes the incoming product line to the 20,000-pound- per-hour tubular preheater (71) so that a

vacuum may be pulled on the system. At the same time, the whey discharge line from the separator (67) is opened to the floor. The steam jet air ejector is started and the water from the cooling tower (114) admitted to the condenser. The cooling tower water-return pump is started, and the water temperature controller (control panel 84) is set to the proper temperature. When the unit is up to full vacuum, water is ad- mitted to the tubular preheater (71). The tem- perature-controller for the tubular preheater is set at 195° F. and the steam turned on. The condensate pumps, (62), (71), (72) (control panel 84), are started. The steam pressure con- troller for the vapor recompressor is set to the proper steam pressure and the steam turned on. At this point, the evaporator will be operating on "Water." The concentrated whey discharge pump is the only evaporator item which remains to be started.

All these functions may be carried out from the control panel (84) except turning on steam to the preheater (71) and evaporator (72), which may be done from valves adjacent to the control panel. These functions are grouped in the upper right-hand part of the control panel.

Centrifugal whey feed pump (65A) is started, forcing the whey at the rate of 20,000 pounds per hour through the vapor-line preheater (62), where it is heated to 110° F., and on through the clarifier (66) and separator (67). The air in the system between the whey feed pump (65A) and the separator is vented to the floor. When the operator notes whey discharging to the floor, he changes the bypass switch to control (71), which shuts off the flow of water to the tubular preheater and closes the valve opening to the floor, thus starting the whey into the tubular preheater.

The 6,000-gallon vertical storage tanks (75, 76) are provided for storing 40-percent total solids whey concentrate before shipping. The proper tank is selected on the control panel (84) by turning the selector switch to "Feed." The city water and 34° F. sweet water are turned on to the concentrated whey plate cooler (74). Sweetwater pump (94A) is turned on. The con- centrated whey system is now ready to receive product from the evaporator (72) .

A continuous reading refractometer is lo-

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

25

ijj

X

n —

CM	1	o
		0

3 CL

LlI I- <

UJ Q Z

o o

		o
	o\ ir)\	0

oso^

XQ-

26

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

cated in the second effect of the evaporator. This device indicates to the operator what the total solids concentration in the second effect is at any time. When the concentration reaches 40-percent total solids, the concentrated whey discharge pump is started. This transfers the concentrated whey through plate cooler (74) to the 6,000-gallon storage tanks. The discharge is adjusted to give a continuous reading of 40-per- cent total solids. The refractometer is checked periodically by the operator, and the discharge of the evaporator is adjusted as needed. The rest of the operation is automatic and continuous.

The Sweetwater inlet valve to the 300-gallon whey cream cooling and storage tank (68) is opened. This will cool the cream to 40° F. When the cream level is above the agitator, the agitator is turned on by pushbutton (68).

The whey processing system is now in full operation.

A centrifugal whey cream pump (70), 25 g.p.m., and positive displacement whey concen- trate pump (78), 100 g.p.m., are suggested for pumping products to tank trucks that are ad- jacent to the processing room.

Tank gages for the whey storage tanks are located on the left side of the control panel (84). These gages will enable the operator to know what the storage situation is at any moment. The gages are equipped with high- and low-level alarms which sound the alarm horn and turn on the pilot lights located just below the tank gage. The alarm may be acknowledged and turned off by pushing the "Alarm Reset" button just be- low the gage. These gages operate on the same principle as those in control panel (82) (fig. 5).

A visual readout is omitted from the whey- processing control panel since there is single usage of all equipment except the 6,000-gallon condensed whey storage tanks. The operator does not need to be informed quickly as to the status of his operating equipment since he does not have to decide on the item of equipment to use next.

The CIP unit (81 A), the controls of which are located in control panel (84), is the same type as that used for the milk processing equip- ment. Its use and operation are discussed else- where.

The double-effect recompression evaporator

provides 3 pounds of evaporation for each pound of steam consumed. The selection of this unit depends upon the balance of operating cost (additional condensing water and fuel required for steam) against capital investment (added cost of double-effect recompression evaporator over single-effect) . In planning whey concen- trating equipment, these costs should be studied.

The vapor-line preheater (62) provides an economical means of raising the temperature of the whey from storage temperature (40° F.) to separating temperature (90°). The steam required for this purpose comes from the second effect on the evaporator (72). Using a vapor-line preheater results in further savings as it reduces the amount of vapor needed to be condensed by the condenser in the evaporator, reducing the size of the cooling tower and re- lated water handling equipment.

Cleaning Equipment

Much of the labor needed to operate a cheese plant is that required to clean equipment and utensils. All equipment and utensils that come in contact with cheese or ingredients used in cheese must be cleaned immediately after use. Proper cleaning methods are important not only for public health reasons, but also to control quality in the finished cheese, especially by combating bacteriophage contamination of the starter and the cheese milk.

Cleaning closed systems, such as storage tanks and HTST pasteurizing units, by circulat- ing methods is a common practice in milk and ice cream plants. These same practices can be followed in cheese plants to reduce labor costs and to make the cleaning operations more effi- cient in use of chemicals, in removing soil, and in sanitizing the surfaces that come in contact with milk. Some equipment, however, such as cheese vats, is not adaptable to circulation cleaning and must be handwashed.

In closed circuits, such as the HTST units, the circulating pump connected with the unit can force the cleaning and sanitizing solutions through the entire system and back to the solu- tion tank. But where the circuit cannot be put under pressure the entire distance, as in wash- ing a milk truck tank or a storage tank, the CIP

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

27

circulating pump delivers the cleaning or sani- tizing solution to a spray ball system mounted at the top of the tank, which circulates the solu- tion, and a separate pump returns the solution to the CIP unit for recirculation.

CLEANED-IN-PLACE (CIP) SYSTEM

Three CIP units (80, 81, 81A) are used in this plant. Two of them (81, 81A) have three-com- partment tanks so that both acid and alkali so- lutions can be used. System 80 has two compart- ments and is used for cleaning the truck tanks; unit 81 is used for pipelines, weigh tanks, stor- age tanks, the HTST unit, and the 300-gallon bulk culture tank (20). Unit 81A is used in the whey department. For cleaning surfaces coming in contact with only cold milk, such as the milk tank trucks, ordinarily only the alkali wash so- lution is used. For cleaning surfaces coming in contact with hot milk, however, both acid and alkali solutions should be used. All the storage tanks have built-in spray balls that give suffi- cient hydraulic action to clean the soiled sur- face.

The CIP unit comes completely assembled. Individual program punchcards are used to give each item of equipment the optimum cleaning cycle. The unit is 41 inches wide, 61 inches long, and 74 inches high. Each stainless steel tank has a maximum working capacity of 165 gal- lons, and the flow of solutions to and from the unit is regulated by air-actuated valves. The CIP unit includes a temperature-control device, a level control, a recorder, air blowdown, and cleaning cycle unit with electropneumatic punchcard program selector located in the proc- ess control panel (82, 84, 85), for each type of cleaning required.

The automatic CIP units clean and sanitize the surfaces of milk processing equipment that come in contact with milk, without dismantling, by controlled circulation of cleaning and ster- ilizing solutions. This is performed by automati- cally regulating the temperature and elapsed time for each phase of the cleaning cycle. A CIP recorder-controlling instrument keeps a record of the cleaning procedure for review by man- agement and health regulatory agencies. The time, temperature, and pressure of the cleaning, rinsing, and sterilizing solutions are recorded

here. The CIP controls are shown on the process control panels (82, 84, 85).

Coupled with the recorder-controller is an electropneumatic punchcard program selector. This device automatically sets the elapsed time, circulating temperature, and proper valve se- quencing for whatever item of equipment is to be cleaned. To clean a particular item, the prop- er punchcard is selected from the card file and inserted into the program selector. The pro- gram may be changed by making up a new punchcard. Once the program is established, there is no need for a variation unless some fac- tors, such as the cleaning compounds, are changed.

Valve sequencing is necessary to insure prop- er cleaning of valve parts as well as branch lines. The program controller sets the sanitary line valves in the proper position for cleaning and also sequences the proper valves to clean the branch lines.

The "Off'-On" pushbutton turns on the power to the control system, and the "Start" button initiates the program selected by the punch- card. The "Stop" button shuts off the program at any point, should the operator wish to do this; the program may again be picked up by the "Start" button. If the operator should de- sire to restart the program from the beginning, the "Reset" button is pushed, followed by the "Start" button. With a quick glance at the pilot lights, located just below the operating push- buttons, the operator knows immediately which phase the CIP unit is in.

A CIP selector switch is provided in the con- trol panel to direct the CIP solutions to the prop- er point for cleaning the equipment item se- lected. This switch also registers on the visual readout of control panel 82.

To clean the various tanks, a swing-elbow connection must be made at the CIP hook-up stations (81B-D), which connects the spray balls to the CIP solution lines. This connection is made by removing the manhole cover of the tank to obtain a key which unlocks the cap cov- ering the solution line. This procedure insures that the tank is properly vented to prevent its collapse from vacuum during the final cold water rinse.

Pipelines are cleaned by making the neces-

28

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

sary hose- jumper connections to complete cir- cuits, followed by circulation of the solutions and valve sequencing by means of the auto- matic CIP units.

Items of equipment in the main plant that will not be cleaned by CIP methods are:

1. Positive displacement pumps

2. Slab curd conveyor

3. Cheese vats

4. Curd milling, salting, and hooping machine

5. Cheese presses

6 Sanitary skids for hoop storage

7. Clarifier*

8. Bulk culture vats located in the starter room

9. Whey clarifier * 10. Whey separator *

* Recently some machines have been placed on the market that the manufacturers claim can be cleaned by CIP methods successfully.

To initiate the cleaning cycle for any storage tank, tank truck, set of milk lines, or process- ing equipment, the punched card for the clean- ing operation for the respective item is inserted into the card-reading unit, the CIP selector is set for the equipment to be cleaned, and the operation set into motion by pushing the proper button. A sample procedure for an open-circuit cleaning procedure for storage tanks follows: Prerinse:

a. Rinse tank automatically filled.

b. Temperature control set initially approxi- mately 100° F.

c. Spray rinse and discharge to drain until clean.

d. Return to rinse tank and circulated 5 min- utes.

Alkali tvash:

a. Solution tank automatically filled.

b. Alkali washing powder added to solution tank by operator.

c. Initial time period set approximately 40 minutes.

d. Temperature control set initially approxi- mately 140° F.

e. Circulate at adjusted temperature and time period, discharging back to solution tank.

f. Cycle ends with all solution returned to solution tank. Rinse :

a. Rinse tank full from last prerinse return.

b. Rinse, temperature same as prerinse, for 5 minutes.

c. Circulate water at tap temperature for 10 minutes and return to rinse tank.

Sanitize: (To be done just before using.)

a. Insert card for sanitizing program.

b. Sanitize chemical powder added to tank by operator.

c. Circulate cold for required period advised by sanitizer manufacturer, which is pro- gramed on card.

d. Discharge to drain.

The CIP procedure using three-tank unit for cleaning hot surfaces is as follows : Prerinse :

a. Rinse tank automatically filled.

b. Temperature control set initially approxi- mately 100° F.

c. Rinse through lines and discharge to drain until clear.

d. Return to rinse tank when clear ; circulate 5 minutes.

Alkali wash:

a. Solution tank automatically filled.

b. Alkali wash powder added to solution tank by operator.

c. Initial time period set approximately 30 minutes.

d. Temperature control set initially approxi- mately 165° F.

e. Circulate at adjusted temperature and time period, discharging back to solution tank.

f. Cycle ends with all solution returned to solution tank.

Rinse:

a. Rinse tank full from last prerinse return.

b. Rinse at 165° F. for 2 minutes maximum; discharge to drain.

Acid wash:

a. Solution tank automatically filled.

b. Acid cleaner added to solution tank by operator.

c. Initial time period set approximately 20 minutes.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

29

d. Temperature control set initially approxi- mately 165° F.

e. Circulate at adjusted temperature and time period, discharging back to solution tank.

Rinse :

a. Rinse tank full from last prerinse return.

b. Rinse same temperature as prerinse for 5 minutes; discharge to drain.

c. Circulate rinse water at tap temperature for 10 minutes; return to rinse tank.

Sanitize: (To be done just before using.)

a. Insert card for sanitizing program.

b. Sanitize chemical powder added to rinse tank by operator.

c. Circulate cold for required period advised by sanitizer manufacturer, which is pro- gramed on card.

d. Discharge to drain.

CLEANED-OUT-OF-PLACE (COP) SYSTEM

Some take-down sanitary pipes and certain pieces of equipment, such as positive displace- ment pumps, clarifiers, curd knives, strainers, dippers, and pails, need to be cleaned out of place. The machines are taken apart and rinsed free of milk remnants, and the various parts and other loose items of equipment are placed in small tanks (79) especially made for COP clean- ing.

The stainless steel tank is 20 inches wide, 18 inches deep and 74V2 inches long. It has a capac- ity of 100 gallons of washing solution. The heat-controlled flow circulation system assures thorough scrubbing of any shaped piece. A cir- culating pump is mounted beneath the tank. A two-way valve in the pump discharge line per- mits recirculation of cleaning or sanitizing so- lution or discharge to the floor. After the parts are rinsed with 100° F. water, cleaning and sanitizing solutions are recirculated through the tank in the same manner as the CIP system operates. The type and strength of the cleaner used will need to be varied according to the de- gree of soiling.

Auxiliary equipment needed with the COP tank includes a small parts basket, clarifier discs rack, sanitary fittings rack, clarifier

truck, and a crane truck for hoisting heavy bowls from clarifier frame. The tanks and cer- tain of the auxiliary items are mounted on casters so that they can be moved where needed.

MANUAL CLEANING AND SANITIZING

The exteriors of all large items of equipment must be kept free of soil. This is done by the operator while or after the equipment is used. Hosing with warm water usually suffices. Some large items of equipment must be handwashed, such as cheese vats and balance tanks.

CLEANING THE WHEY-HANDLING EQUIPMENT

CIP unit 81A, located in the whey-handling department, is used for cleaning the whey- receiving tanks, the evaporator, the heaters, the condensed whey plate cooler, the condensed whey storage tanks, the pipeline that brings the whey from the cheese vats to the whey han- dling department, and the whey cream storage tank. The positive displacement pumps, clarifier, and separators are cleaned out of place, though some of the newer clarifiers and separators can be cleaned in place, according to the manufac- turer.

The methods used for cleaning these items are essentially the same as those used in the main plant using unit (81) with the controls located in the control panel (82).

Loading Out

The cheese is loaded out from an enclosed loading dock which is 10 feet deep and 110 feet long. The dock has two loading doors so that two trucks may be loaded at a time.

The cheese is put into the truck on the same pallets on which it is stored in the 40° F. stor- age room. The pallets are sized so that they can be placed in the delivery truck in two rows stacked two high. A forklift is used to load the trucks.

About 40 pallet loads of cheese are loaded out on an average day. Since the buyers provide their own trucks which differ considerably in capacity, the volume loaded out per truck var- ies from day to day. Generally, no more than three or four trucks are loaded in one day.

30

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

LABOR REQUIREMENTS

A total of 22 workers are needed to operate an automated plant of this size, excluding office workers. Each worker will work an 8-hour day, 5 days a week, with a oO-minute lunch period, except for the plant superintendent and engi- neer who will have 1-hour lunch periods.

Plant Workers Needed

The workers and their principal duties are as follows :

No. Wo7'ker PrinciTpal duties

1. Superintendent Supervises all plant oper- ations, makes records, hires workers, assigns jobs.

Maintains all equipment in plant.

Assists superintendent and takes short relief assignments. Receives milk, does clean- ing and yard work. Takes care of cheese vats

1 and 6.

Takes care of cheese vats

2 and 7.

Takes care of cheese vats

3 and 8.

Takes care of cheese vats

4 and 9.

Takes care of cheese vat 5, 5 days per week, fin- ishes vats 6, 7, 8, 5 days per week, and vat 9, 2 days per week. Inserts bandages in hoops.

Hoops cheese and places on conveyor. Dehoops.

Stacks cheese for drying. Takes care of all starters

5 days per week. Works in laboratory.

Works in laboratory.

2. Engineer

3. Foreman

4. Receiver

5. Cheesemaker

6. Cheesemaker

7. Cheesemaker

8. Cheesemaker

9. Cheesemaker

10. Assistant to

cheesemaker

11. Assistant to

cheesemaker

12. Assistant to

cheesemaker

13. Stacker

14. Starter

technician

15. Laboratory

technician

16. Laboratory

technician

18. Whey plant

operator

19. Whey plant

worker

20. Relief man

21. Relief man

22. Relief man

17. Storeroom clerk Takes care of storeroom, receiving and shipping of merchandise ; turns cheese in p.m. Separates whey and con- denses whey. Separates, condenses, cools whey; does maintenance. Relieves workers 5, 10,

12, 16, 17, one day each. Relieves workers 6, 7, 11,

13, 18, one day each. Relieves workers 3, 4, (2 days) 8, 9 (1 day).

In assigning relief workers, job assignments were rotated so that these workers would obtain broader experience. Rotating jobs also provides a method for training new workers for the va- rious types of jobs in the plant.

Work Schedules

Work schedules for the specified plant em- ployees are as follows : Worker No. 1 (Superintendent) : Hours to be General supervision of all arranged. operations and all workers.

Hires workers and assigns them to their duties. Makes necessary reports.

Worker No. 2 (Maintenance engineer) :

2 days per week,

7 :00 a.m. - 3 :30 p.m. Care of all automatic

3 days per week machines and their 12 m. - 8 :30 p.m. controls, keeping them

oiled, adjusted, and in good repair.

Worker No. 3 (Foreman) : 7:00 a.m. -3:30 p.m.

7:00 Sanitize equipment for re-

ceiving milk, 8:00 Start pasteurizer.

8:05 Pump starter into milk line

leading to cheese vat 1. 8:55 Prepare rennet for vat 1.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

31

Worker No. 3 — Continued : Worker No. 3 — Continued :

9:00	Switch valve on milk line		from vat 6 to vat 7. Add
	from vat 1 to vat 2. Add		rennet to vat 6, agitate
	rennet to vat 1, agitate		milk, remove paddles.
	milk, remove paddles.	2:05	Pump starter into milk line
9:05	Pump starter into milk line		leading to vat 7.
	leading to vat 2.	2:30	Assist cheesemaker in cut-
9:30	Assist cheesemaker in cut-		ting curd in vat 6.
	ting curd in vat 1.	2:35	Place bandages in hoops for
9:55	Prepare rennet for vat 2.		vat 2.
10:00	Switch valve on milk line	2:55	Prepare rennet for vat 7.
	from vat 2 to vat 3. Add	3:00	Switch valve in milk line
	rennet to vat 2, agitate		from vat 7 to vat 8. Add
	milk, remove paddles.		rennet to vat 7, agitate
10:05	Pump starter into milk line		milk, remove paddles.
	leading to vat 3.	3:05	Pump starter into milk line
10:30	Assist cheesemaker in cut-		leading to vat 8.
	ting curd in vat 2.	Worker No. 4
10:55	Prepare rennet for vat 3.	(Receiver) :
11:00	Switch valve on milk line	7 :15 a.m. - 3 :45 p.m.
	from vat 3 to vat 4. Add	7:15	Check equipment for receiv-
	rennet to vat 3, agitate		ing milk.
	milk, remove paddles.	7:30	Start receiving milk and
11:05	Pump starter into milk line		washing bulk milk delivery
	leading to vat 4.		trucks.
11:05	Lunch.	11:30	Lunch.
11:30	Assist cheesemaker in cut-	12:00m.	Receive milk.
	ting curd in vat 3.	2:00	Clean equipment and take
11:30	Relieve receiving man for		care of premises.
	lunch.	Worker No. 5
11:55	Prepare rennet for vat 4.	(Cheesemaker) :
12:00 m.	Switch valve on milk line	9:30 a.m. -6:00 p.m.
	from vat 4 to vat 5.	9:30	Operate vat 1 from curd
12:05	Pump starter into milk line		cutting to vat washing.
	leading to vat 5.	2:00	Lunch.
12:30	Assist cheesemaker in cut-	2:30	Operate vat 6 from curd
	ting curd in vat 4.		cutting to 4-high stacking.
12:55	Prepare rennet for vat 5.	Worker No. 6
1:00	Switch valve on milk line	(Cheesemaker) :
	leading from vat 5 to vat 6.	10:30 a.m. -7	:00 p.m.
	Add rennet to vat 5, agitate	10:30	Operate vat 2 from curd
	milk, remove paddles.		cutting to vat washing.
1:05	Pump starter into milk line	3:00	Lunch.
	leading to vat 6.	3:30	Operate vat 7 from curd
1:30	Assist cheesemaker in cut-		cutting to 4-high stacking.
	ting curd in vat 5.	Worker No. 7
1:35	Place bandages in hoops for	(Cheesemaker) :
	vat 1.	11:30 a.m. -8	:00 p.m.
1:55	Prepare rennet for vat 6.	11:30	Operate vat 3 from curd
2:00	Switch valve on milk line		cutting to vat washing.

32

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

Worker No. 7 — Continued : Worker No. 10 — Continued :

3:55	Prepare rennet for vat 8.		conveyor to press of vat 4.
4:00	Switch valve from vat 8 to	5:30	Dress bandages on hoops at
	vat 9. Add rennet to vat 8,		press of vat 3.
	agitate, remove paddles.	5:45	Put bandages in hoops for
4:05	Lunch.		vat 5.
4:35	Operate vat 8 from curd	6:15	Move hoops from overhead
	cutting to 4-high stacking.		conveyor to press of vat 5.
Worker No. 8		6:30	Dress bandages on hoops at
(Cheesemaker) :			press of vat 4.
12:30 to 9:00 p.m.	6:45	Put bandages in hoops for
12:30	Operate vat 4 from curd		vat 6.
	cutting to vat washing.	7:15	Lunch.
4:55	Prepare rennet for vat 9.	7:45	Put bandages in hoops for
5:00	Shut off pasteurizer for vat		vat 7.
	9, add rennet, agitate milk,	8:15	Move hoops from overhead
	remove paddles.		conveyor to press of vat 7.
5:05	Lunch.	8:30	Dress bandages on hoops at
5:35	Operate vat 9 from curd		press of vat 6.
	cutting to vat washing.	8:45	Put bandages in hoops for
	On 8-vat days (Wed.,		vat 8.
	Thurs., Fri., Sat.) wash	9:15	Move hoops from overhead
	walls of cheese room'.		conveyor to press of vat 8.
Worker No. 9		9:30	Dress bandages on hoops at
(Cheesemaker) :			press of vat 7.
1:30-10:00 p.m.	9:45	Put bandages in hoops for
1:30	Operate vat 5 from curd		vat 9.
	cutting to vat washing.	10:15	Move hoops from overhead
5:50	Start CIP.		conveyor to press of vat 9
6:00	Lunch.		on Wed., Thurs., Fri., and
6:30	Operate vat 6 from final		Sat.
	4-high turn to vat washing.	10:30	Dress bandages on hoops at
7:00	Operate vat 7 from first		press of vat 8.
	4-high turn to vat washing.	10:45	Wash milling, salting, and
8:00	Operate vat 8 from first		hooping machine.
	4-high turn to vat washing.	Worker No. 11
9:00	Operate vat 9 from first	(Assistant to cheesemaker) :
	4-high turn to vat washing.	3 days per week ;
Worker No. 10		1:00-9:30 p.m.
(Assistant to cheesemaker) :	2 days per week ;
3:45 p.m. - 12	:15 a.m.	1:45 -10 :15 p.m.
3:45	Put bandages in hoops for	1:00	Prepare and sanitize mill-
	vat 3.		ing, salting, and hooping
4:15	Move hoops from overhead		machine.
	conveyor to press of vat 3.	1:10	Fill salt hopper on machine.
4:30	Dress bandages on hoops at	1:15	Move hoops of vat 1 from
	press of vat 2.		day before from press to
4:45	Put bandages in hoops for		overhead conveyor.
	vat 4.	1:45	Hoop curd in vat 1 and place
5:15	Move hoops from overhead		on overhead conveyor.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

33

Worker No. 11 — Continued: Worker No. 11 — Continued:

2:15	Move hoops from overhead	9:30	Refill salt hopper.
	conveyor to press of vat 1	9:45	Hoop curd in vat 9, place on
	and move hoops of vat 2		overhead conveyor.
2:45	from day before from press to overhead conveyor. Hoop curd in vat 2 and place	Worker No. 12 (Assistant to cheesemaker) :
	on overhead conveyor.	1:00-9:30 p.m.
3:15	Move filled hoops from con- veyor to press of vat 2 and move hoops of vat 3 from	1:00	Fill hoop washer and pre- pare area for dehooping and washing.
	day before from press to	1:15	Dehoop, wash hoops from
	overhead conveyor.		vat 1 of day before.
3:45	Hoop curd in vat 3 and place	1:45	Paraffin vat of daisies.
	on overhead conveyor.	2:15	Dehoop, wash hoops of vat
4:15	Move hoops of vat 4 from		2 from day before.
	day before from press to	2:45	Paraffin vat of daisies.
	overhead conveyor.	3:15	Dehoop, wash hoops from
4:30	Assist cheesemaker cut		vat 3 of day before.
	curd in vat 8.	3:45	Paraffin vat of twins.
4:35	Refill salt hopper.	4:15	Dehoop, wash hoops from
4:45	Hoop curd in vat 4 and place		vat 4 oi day before.
	on overhead conveyor.	4:45	Paraffin vat of twins.
5:15	Lunch.	5:15	Dehoop, wash hoops from
5:45	Hoop curd in vat 5 and place		vat 5 of day before.
	on overhead conveyor.	5:45	Lunch.
6:00	Check CIP and COP.	6:15	Dehoop, wash hoops of vat
6:20	Move hoops of vat 6 from		6 from day before.
	day before from press to	6:45	Paraffin vat of twins except
	overhead conveyor.		on Mon., Tues., Fri., and
6:45	Hoop curd in vat 6 and place on overhead conveyor.		Sat. (On these days, clean dry storage room and dry-
7:15	Move filled hoops from over-		ing racks.)
	head conveyor of press of	7:15	Dehoop, wash hoops of vat
	vat 6 (worker 10 eats		7 from day before.
	lunch) .	7:45	Paraffin vat of cheddars.
7:30	Dress bandages on hoops at press of vat 5 (worker 10	8:15	Dehoop, wash hoops of vat 8 from day before.
	eats lunch) .	8:45	Paraffin vat of cheddars.
7:45	Hoop curd in vat 7 and place on overhead conveyor.	9:15	Dehoop, wash hoops of vat 9 from day before.
8:15	Check CIP and COP.	Worker No. 13
8:20	Move hoops of vats 8 and 9	(Stacker) :
	from day before from press	2:00-10:30 p.m.
	to overhead conveyor.	2:00	Rem.ove hoops from washer
8:45	Hoop curd in vat 8 and place		(vat 2).
	on overhead conveyor.	2:45	Stack cheese on racks (vats
9:15	Finish CIP and clean COP.		1 and 2).
	Job ends at 9 : 30 p.m. 3 days	3:00	Help No. 12 paraffin vat of
	each week.		daisies.

34

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

Worker No. 13 — Continued:

3 :15 Remove hoops from washer

(vat 3).

3:45 Stack cheese on racks (vat

3) .

4:00 Help No. 12 paraffin vat of

twins.

4:15 Remove hoops from washer

(vat 4).

4:45 Stack cheese on racks (vat

4) .

5:00 Help No. 12 paraffin vat of

twins.

5:15 Remove hoops from washer

(vat 5). 5:45 Lunch.

6:15 Remove hoops from washer

(vat 6).

6:45 Move 2 vats (5 and 6) of

blocks to cooler. 7:00 Help No. 12 paraffin vat of

twins. (On Mon., Tues.,

Fri., and Sat., clean walls of

cheese cooler.) 7:15 Remove hoops from washer

(vat 7).

7 :45 Stack cheese on racks (vat

7) .

8:00 Help No. 12 paraffin vat of

Cheddars.

8:15 Remove hoops from washer

(vat 8).

8:45 Stack cheese on racks (vat

8) .

9:00 Help No. 12 paraffin vat of

Cheddars.

9:15 Remove hoops from washer

(vat 9*). Dehoop remain- der of vat 9.

9:45 Stack cheese on racks (vat

9*).

*0n 8-vat days, wash one wall of hoop storage room each day instead of work shown on vat 9. 10:00 Drain hoop washer, wash

floor.

Worker No. 14 (Starter technician) : Hours to be On 6th day checks batch of arranged. culture set on 5th day. Has

complete charge of the starter program.

Workers No. 15 and 16 (Laboratory technicians) : Hours to be ar- Duties outlined in section ranged. Work of on "How the Plant Oper- each technician ates," which describes the complements that functions of the laboratory, of the other; hours are arranged so one is in labora- tory each of 6 working days.

Worker No. 17 (Storeroom clerk) :

Hours to be Loads out cheese.

arranged. Checks in freight.

Supplies cheeseboxes and paraffin to dehooping and paraffining rooms. Supplies 10-pound paper boxes to block-wrapping room.

Furnishes haulers with pa- tron supplies (orders made up the day before) . Supplies starter room with powder needs. Weighs out chemicals for CIP and COP systems. Prepares shipping orders and receiving records. Supplies salt to curd-milling machine.

Turns round cheeses on racks in afternoons. Dresses bandages on vat 1. Moves hoops of vat 5 from day before from press to overhead conveyor. Moves hoops of vat 7 from day before from press to overhead conveyor.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

35

Worker No. 18 (Whey-plant operator) : 11:00 a.m.- Set up whey clarifier and 7:00 p.m. separator.

Assembles open fittings and sanitizes separator, evapo- rator, plate cooler and tanks.

Starts separator, evapora- tor, and plate cooler ; checks boiler and compressors. Checks solids, draws off condensed whey, cools con- densed whey, and pumps into storage tanks. Checks acidity of raw whey every hour.

Checks automatic solids test reading on condensed whey every half hour. Checks temperature of heated whey, evaporator, vapors, cooled whey, and cooled whey cream every half hour.

Checks whey cream thick- ness.

Checks ammonia pressures. Checks boiler operation, wa- ter level, and pressure. Checks all bearings periodi- cally for malfunction. Checks all equipment main- tenance possible while in operation.

Pumps condensed whey to tank truck.

Pumps whey cream to tank truck.

CIP cleans condensed whey storage tanks and whey cream tanks.

Eats lunch while equipment is under normal operation.

Worker No. 19 (Whey-plant worker) : 7:00 p.m.- Finishes whey evaporation 3:30 a.m. (on 9-vat days).

Pumps balance of con- densed whey from evapora-

Worker No. 19 — Continued :

tor through plate cooler and into condensed whey stor- age tanks.

Bypasses clarifier and sepa- rator^ and circulation cleans whey storage tanks, heat- ers, evaporator, plate cool- er, and sanitary lines. COP cleans clarifier and separator.

Adjusts machinery, replac- es worn parts. Checks boiler blowdown, boiler cleaning, and burner adjustment.

Adds ammonia to compres- sors.

Scrubs floors daily and walls and ceiling as needed in whey-handling area, refrig- erator room, boiler room, and shop. Workers No. 20 - 22 (Relief workers) : Hours to be To maintain a 40-hour work arranged. schedule for this plant, 3

relief workers are needed. Their hours will be as re- quired to meet the schedule of the regular workers giv- en above.

To show the sequence of operations in making a batch of cheese and to better explain each worker's part in the cheesemaking process, the following timetable is given. The other vats of cheese follow the same schedule at 1-hour intervals until all eight (or nine) batches are completed.

A.M.
8:00	Start filling vat ; begin add-
	ing starter.
8:10	Finish adding starter.
9:00	Vat filled ; rennet added.
9:30	Curd cut.
9:40	Paddles detached ; agitators
	started.
9:50	Steam on in jacket.
10:30	Steam off in jacket.

Unless self -cleaning clarifier and separator are used.

36

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

11:20	Draw half of whey ; run	1:30	Turn blocks.
	acidity test on whey.	1:35	Run aciditv test on whev
11:25	Stop agitators ; start ditch-	1:40	Pile curd blocks on belt con-
	ing (making trough) .		veyor. Salt added to milling
12:00	Draw remainder of whey ;		machine.
	run acidity test on whey.	1:45	Start bandacinff boons*
P.M.			start milling machine and
12:05	Cut curd into blocks.		hoop filling.
12:10	Turn blocks.	1:50	Wash vat.
12:15	Turn blocks.	1:55	Finish bandaging hoops.
12:20	Turn blocks.	2:15	Finish milling, salting, and
12:25	Turn blocks.		hooping ; put filled hoops on
12:30	Cut blocks in two parts.		presses.
12:35	Pile blocks 2 high.	2:30	Apply pressure to hoops.
12:40	Turn blocks.	3:30	Adjust bandages.
12:45	Pile blocks 3 high.	3:45	Apply pressure to hoops.
12:50	Turn blocks.	Following day
1:00	Pile blocks 4 high.	1:15-1:45	Remove hoops from press
1:10	Turn blocks.		and place on overhead con-
1:20	Turn blocks.		veyor to the dehooper.

COSTS AND POSSIBLE BENEFITS OF LABOR-SAVING DEVICES

The equipment required for the automated Cheddar cheese plant to minimize labor require- ments and estimated costs of the items based on 1968-69 prices are as follows :

Dollars

Weighing tank load cell system 8,000

Three CIP units and CIP pipe 24,000

Automatic control instruments 25,000

Milling and salting machine 52,000

Conveyor system for carrying hoops 8,000

Automatic hoop washer and conveyor 4,000

Automatic block cutting, wrapping, boxing . 15,000

Mechanical agitators for cheese vats 15,000

Load cells for weighing tanks 5,000

Tank gages 9,000

Control panels with switches 15,000

Additional sanitary pipeline and air-operated

valves 15,000

Controls for boilers and refrigeration units 5,000

Subtotal 200,000

Additional refrigeration machinery, and air temperature and humidity controls in starter room, drying room, and plant follow :

Dollars

Two 100-ton compressors 20,000

One 198-ton chilled water unit 10,000

One 30-ton air conditioner 3,200

Two 15-ton air conditioners.. 4,600

Two 45-ton air conditioners 8,800

One 22y2-ton air conditioner 2,300

One 12-ton air conditioner with high frequency

filters 2,400

Pumps and piping 10,000

Subtotal 62,000

Total 262,000

Thus, the estimated cost of the equipment would be $262,000 greater than that for the nonautomated plant.

The automated plant could operate with an estimated 21 fewer workers than a properly ar- ranged and operated nonautomated one han- dling a similar volume. Based on an assumed costs of $6,500 annually per worker (salary plus fringe benefits), the annual savings in labor would be $136,500 for an automated plant. If 20 percent is allowed annually for ownership and operating costs (depreciation, interest, insur- ance, taxes, maintenance, and power), the costs would amount to $52,400 and an annual saving of $84,100 would result.

Production per man-hour of labor should be higher in the automated than in the nonauto- mated plant. The production on a peak day in the automated plant would be about 88 pounds of cheese per man-hour compared with 45 pounds per man-hour in a nonautomated plant.

Machine-controlled operations should reduce in-plant production losses and provide a more uniform cheese than that obtained in a nonauto- mated plant using conventional equipment. No data, however, are available for the savings that would be realized from these items.

FlGUitE 9.— A suggested refrigeration system for an automatedcheddar cheese plant handling 80U,000 pounds of milk weekly.

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

37

APPENDIX: REFRIGERATION, HEATING, VENTILATING, AND AIR CONDITIONING

Refrigeration System

The refrigeration system (fig. 9) for the plant should be adequate to cool milk and whey products, to maintain the required room tem- perature and humidity in the drying room and 40° F. storage room, and to handle the air- conditioning load. All of the refrigeration is supplied by an ammonia refrigeration system, except that for the drying room. This room is on a separate Freon condensing unit so that the humidity here can be closely controlled.

The refrigeration calculations are based partly on data contained in the "Mechanical Engineers' Handbook," "Heating, Ventilating, and Air Conditioning Guide," and "Refrigera- tion Engineering Application Data."'*

Starter in 300-gallon vats (24, 25), whey passing through a plate heat exchanger (61), and concentrated whey passing through a plate heat exchanger (74) are cooled by 34° F. sweet water. The sweet water is recirculated through Sweetwater cooling unit (91). The air- conditioning units (122, 123, 124, 124A, 125; are refrigerated by recirculating chilled water at 38°. This water is recirculated through chilled water cooling unit (92). These two cooling units are identical except that one is sized to maintain a temperature of 34° and the other 38°. To distinguish between the two units, one is referred to as a sweetwater cooling unit (34° water) and the other a chilled water cooling unit (38° water).

These cooling units consist of corrugated stainless steel plates over which water flows from a distributing trough on top to a collect- ing tank on the bottom. The water level is main- tained by a float control in the collecting tank. Ammonia is evaporated inside the corrugated sections, thus cooling the water. The ammonia flow is controlled by a gravity-type flooded ammonia control with ammonia float valve to

' Marks, Lionel S. mechanical engineers' hand- book, 4th ed., illus. 1941 ; American Society of Heating AND Air Conditioning Engineers, heating, ventilat- ing and air conditioning guide. 1947; Segal, S. Charles, refrigeration load calculations — • II. tem- peratures below 32° F. refrig. engin. applic. data 12. Refrig. Engin. Vol. 39, No. 4, Sec. 2. April 1940.

control the incoming liquid and a back pressure regulating valve to control the ammonia tem- perature within the corrugated sections. Pumps (93, 94, 94A, 95, 96, 97, 98) are used to circulate the water through the equipment.

The raw milk storage tanks (5, 6, 7) are equipped with cold-wall sections which consist of a corrugated stainless steel sheet welded to the outside of the inner jacket on the bottom part of the tank. Liquid ammonia is admitted to these coils by combination solenoid-thermostatic expansion valves, which will maintain the milk at 38° F. The temperature of the ammonia in the refrigerated section is controlled by an ammonia back pressure regulating valve. The flow of ammonia may be turned off by a push- button in control panel (82). The refrigeration load of these tanks is small in comparison to other loads and occurs principally when other loads are off. Therefore, it is not included in the calculations which determine the size of the ammonia compressor equipment.

The cold storage room is maintained at the desired temperature (40° F.) by eight cooling units (90) suspended from the ceiling. Each unit has coils in which ammonia evaporates, cooling them. Air is blown over these coils by a fan in the unit to cool the room. The flow of ammonia through the coils is controlled by a thermostatic expansion valve, and the tempera- ture of the ammonia in the coil is controlled by an ammonia back pressure regulating valve.

The factors used in determining the sizes of equipment suggested for the plant are described below. The refrigeration requirements pre- sented here are offered as a guide only, since many conditions, such as temperature differ- ences, types of building materials used, and plant location, affect the requirements of a particular plant. Operators planning to build new plants or remodel present facilities should consult local refrigeration engineers for their specific requirements.

SWEETWATER COOLING UNIT (91) LOADS

These loads would be based on the plant's peak operating capacity. This capacity occurs

38

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

when starter, whey, and whey concentrate are being cooled at the same time. The starter is cooled from 70° to 40° F. in 1 hour. Prelimi- nary cooling in the plate heat exchangers is done with 68° well water. The formula for hourly B.t.u. (British thermal units) requirements is:

B.t.u. _ Weight of product y_ Temperature Specific per hr. ~ per hr. change heat

Equip- ment

No. Product

Rate of Temper- cooling ature per hr. change

Specific heat

B.t.u. per hr.

24, 25 . .. Starter

61 Whey

74 Cone, whey

(40% TS)

Lb.

5,160 20,000 3,000

" F. 70-40 76-40 90-40

1.0 1.0 .9

154,800 720,000 135,000

Total .1,009,800

10 percent for line and pumping loss 100,980

Total required 1,110,780

The compressor capacity required would be:

1,110,780 12,000

92.5 tons.

CHILLED WATER COOLING UNIT (92) LOADS

The chilled refrigeration loads in tons for the seven air-conditioning units (122-125) are listed below. The loads are as recommended by equipment manufacturers for the size of room and type of equipment in the room.

Unit number

Rooms where used

Volume of area

Air circu- lated

Chilled water refrig- eration load

Cu. ft.

Laboratories, offices,

and office toilets 29,770

Culture, mother culture 12,096 Paraffining, hoop wash 35,104 Restrooms, lunch- rooms, locker rooms 24,784 125(3) Cheese processing,

pasteurizing 210,560

Total ~~~~~~~

122

123 124 124A

C.f.m. Tons

7,500 4,000 10,000

30 12 30

5,000 15 60,000 90

177

40" F. ROOM COOLING UNIT (90) LOADS

The factors which determine the refrigeration requirements of the cold storage room are: (a) Heat gain through walls, ceiling, and floor, (b) heat gain through air changes in the coldroom (c) heat gain from electrical energy, and (d) heat gain from cheese held in the room. A heat gain would also be incurred from workers and forklift trucks which enter the room; however, for the proposed plant this would be only one or two people at a time, depending on the load-in or load-out situation at the time. Thus, the heat

gain from this source would be comparatively small and is included in the suggested safety factor for the room. In these calculations, the peak average hourly load for all factors is com- puted with the exception of the heat gain from the cheese entering and being held in the room. The cheese will not give up all its heat the first hour; therefore, the average for a 24-hour period is used.

(a) Heat gain through walls, ceiling, and floor is calculated by the formula shown below. The calculations are based on a coldroom tem- perature of 40° F. and outside temperature of 95° F. An average overall coefficient of heat transmission for walls, floor, and ceiling of 0.0756 B.t.u. per hour per square foot per de- gree F, temperature difference is suggested. This is equivalent to a wall section of 8 inches of brick and 4 inches of insulation. The cold- room for the suggested plant would have a sur- face area of :

Sq. Ft.

Walls = 42x17x2 + 112x17x2 = 5,236 Ceiling = 112x42 = 4,704

Floor = 112x42 = 4,704

Total surface = 14 644

Heat gain through walls, floor, and ceiling (B.t.u. per hour)

14,644 X 0.0756 X 55 = 60,890 B.t.u. per hour.

(b) Heat gain from air changes is calculated by the following formula. It is estimated that a room of this type would have one air change every 2 hours, or 0.5 change per hour. This would occur principally when loading in or out of the room.

Surface

0.0756 (B.t.u. per

Tempera- area ^ 1^7,','^ ture

^(^^"^^^"^ square ^^ange feet) l^^f;^^ CF.)

Volume

Heat gain

from air ^^^^ changes = feubT ^ hour per feet) cu. ft.)

2.53

(B.t.u. per

X

Number of air changes

hourr^^"" '^"•f*-) per hour

40x16x110x2.53x0.5 = 89,056 B.t.u. per hour, (c) Heat gain from electrical energy is from electrical motors and lights. It is assumed that 4 horsepowers (hp.) are used on the eight cool- ing units. For this calculation, 1 hp. equals 3,700 B.t.u. per hour.

Heat gain from motors

(B.t.u. Motor

per hour) = horsepower x 3,700

= 4 X 3,700 = 14,800

B.t.u.

per hour

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

39

It is assumed that 1,400 watts of electricity are used for lights; 1 watt-hour equals 3.42 B.t.u. per hour.

Heat gain from lights (B.t.u.

per hour) = Number of watts X 3.42

= 1,400 X 3.42 = 4,788

B.t.u. per hour

Total heat gain from electrical energy = 19,588 B.t.u. per hour.

(d) Heat gained from product entering the room is determined from the maximum amount of cheese entering, or 17,366 pounds per day. Eighty percent of this comes from the drying room, and 20 percent is in prints, going directly to the 40° F. cold storage room from wrapping and boxing. To determine the refrigeration re- quired, it is estimated that the average blend temperature of the cheese, packages, and pal- lets from the drying room is 60° F., and that this temperature coupled with the estimated specific heat factor results in an accurate esti- mate of the heat gain due to cheese entering the room. The blend temperature of the prints is estimated to be 80° F. The formula for deter- mining the heat gain from products entering the room is :

Heat gain from cheese (B.t.u. per hr.)

- Weight of cheese x temp, change X spec, heat 24 hours

_ 17,366 X 20 X 0.8 X 0.6 + 17,366 X 40 X 0.2 X 0.6 ~ 24 24

= 6,946 + 3,473 = 10,419 B.t.u. per hour.

The following is a summary of heat gains in the cold storage room :

B.t.u.

Walls, ceiling, floor 60,890

Air changes 89,056

Electrical energy 19,588

Cheese entering room 10,419

Total 179,953

10 percent allowance 17,995

Total requirements 197,948

Since the room cooling units (90) are to op- erate only 16 hours per day to provide 8 hours for automatic defrosting, the load of 197,948 B.t.u. must be removed from the room in two- thirds of an hour. Therefore, the cooling unit must remove 197,948 X 3 h- 2, or 296,922 B.t.u. per hour.

The total refrigeration load would be :

296,922 ^, „ , 12:000- = 2^-^

The eight cooling units (90) suggested have a capacity of 3.1 tons each, or a total of 24.8 tons.

The total refrigeration requirements are:

Tons

Sweetwater cooling unit (91) 92.5

Chilled water cooling unit (92) 177.0

40° F. cold storage room 24.7

Total 294.2

To handle the refrigeration load, three 100- ton (100, 101, 102) and one 25-ton (99) ammo- nia compressors are suggested. The 100-ton compressors would operate at 40-pounds suction pressure and 185-pounds condensing pressure and would require 100-hp. electric motors. The 25-ton compressor would operate at 35-pounds suction pressure and 185-pounds condensing pressure and would require a 30-hp. electric motor.

The 25-ton compressor (99) is connected to the 40° F. storage room. It will start and stop automatically by a room thermostat, set to turn on at 40° and off at 38°. The thermostat will also shut off the supply of ammonia to the coils. The air circulation fans continue to run, thus automatically defrosting the coils by cir- culating room air over them. The suction line from the cooling units (90) to the 25-ton com- pressor is cross connected to the suction line from the chilled water and sweetwater units so that the other ammonia compressors may be used on the 40° F. room should the 25-ton com- pressor be shut down for repairs.

The three 100-ton compressors are the multi- cylinder type with 75- and 50-percent capacity controls. Thus, the three compressors provide a variable capacity of 50 to 300 tons at 25-ton in- crements. This capacity control is automatic by a pressure switch, which will maintain the suc- tion pressure in a range of 35 to 40 pounds. As a load increases in an air-conditioning unit or any of the sweetwater refrigerated machinery, or on a cold-wall tank, the suction pressure will rise. This rise is sensed by the pressure switch, which adjusts the capacity controls to suit the condition. Except for turning the compressors on, the operation is fully automatic.

During the winter only one 100-ton compres- sor would be used. During periods of moderately warm weather two 100-ton compressors are re- quired, and for hot weather all three 100-ton

40

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

compressors would be on the line. The number of compressors used may also vary with the time of day, since at night in hot weather only one unit would be required.

To condense the ammonia, two 165-ton evap- orative condensers (105, 106) are suggested. They are located outside the refrigeration room on concrete piers high enough that the liquid ammonia will drain by gravity to the 24-inch by 16-foot receiver (112) . Since many cheese plants are located in areas which have severe cold weather in winter, the water from the sump pan on the evaporative condensers can be drained by gravity to the sump tank (108). Draining this water prevents the pumps and water from freez- ing, since they are located just inside the refrig- eration room. During seasons of rapid change in temperature, this is advantageous, as the con- densers can run dry at night when it is cold and the water pumps will start automatically during the day when the outside temperature rises. The pumps and piping never freeze, since when they are off all water drains to the sump tank.

The condensing pressure is controlled by pres- sure switches which start the fan and pump motors on a pressure rise. The first evaporative condenser fan would turn on at 150 p.s.i. (pounds per square inch) and off at 135 p.s.i. The second evaporative condenser would turn on at 155 p.s.i. and off at 140 p.s.i. The pumps on the first and second evaporative condensers would be set to turn on at 160 and 165 p.s.i., re- spectively, and off at 145 and 150 p.s.i. Thus, under low loading conditions, or cold outside air, the units would run dry.

DRYING ROOM AIR-CONDITIONING UNIT (131)

This unit differs from the other air-condition- ing units in that it has a reheat coil; that is, the air first passes through a heating coil, then a cooling coil, followed by a second heating coil and a steam injection humidifying unit. A reheat coil is required because the humidity must be controlled within a very narrow range. The unit uses 15 percent makeup air all seasons of the year and is designed to maintain a temperature of 55° F. and a relative humidity of 70 percent at all times. The cooling coil is refrigerated by a 15-ton Freon condensing unit (128) located in the refrigeration room. This unit is controlled

automatically by a humidistat and thermostat located in the drying room.

In winter, outside air, which is 10° F. and 80- percent relative humidity, when heated to 55° without the addition of moisture, would have a relative humidity of approximately 12 percent. Thus, under these conditons, heating is per- formed partly by the first heating coil, with final heating from the humidifying steam injection unit to result in the discharge of air at 55° and 70-percent relative humidity. In summer, outside air at 95° F. and 50-percent relative humidity, when cooled to approximately 74°, is saturated with moistui-e; that is, it has a relative humidity of 100 percent. Under these conditions, further cooling from 74° F. condenses moisture out of the air. To discharge air from the air-condition- ing unit at 55° and 70-percent relative humid- ity, the air should be cooled to approximately 45° to condense sufficient moisture so that upon reheating to 55° the relative humidity will be 70 percent. Thus, in winter the first heating coil and humidifier ai-e used; in summer the cooling coil and reheat coil are used. The above temper- ature and humidity conditions are for outside or makeup air and are, of course, tempered by the use of 85-percent recirculated air.

The use of this air-conditioning unit (131) permits maintaining constant temperature and humidity conditions in the drying room at all times.

Heating System

A heating system is required to provide steam for processing milk, cheese, and whey, as well as for heating water for cleaning equipment, and for heating the building. A heating system should be adequate to handle the peak require- ments. These requirements depend to some ex- tent on the climate of the area in which the plant is located. Thus, heating data provided herein are offered as a guide only. Operators of cheese plants planning to build new plants, or remodel their present facilities, should contact local heating engineers regarding their heating requirements.

The basic formula for determination of the

B.t.u. requirements for heating milk products is:

p.. Weight of Tempera- o^pHfir

Der hr = P^^^"^* >< ^""^^ ^ heat P^^^"^- perhr. change

Tabulated below are the B.t.u. requirements

AUTOMATION OF DAIRY PLANTS PROCESSING CHEDDAR CHEESE

41

for heating the various milk products handled in this plant, based on this formula. The whey vaporline preheater (62) receives its heat from the double-effect recompression evaporator (72) and is therefore not included. The B.t.u. require- ments for operating the double-effect recom- pression evaporator are those recommended by manufacturers of this type of equipment. The culture vats (24, 25) heat through the tem- perature range indicated in 45 minutes ; there- fore, the B.t.u. requirements are adjusted to include this. The cheese vats (29-37) are heated through their range in 35 minutes con- secutively ; therefore, only one vat is included. The contents of the cheese vat include, in addi- tion to the milk, 10 gallons of water (rennet addition) plus 1.00 percent starter.

Equip-		Amount	Temper-	Spe-
ment		of	ature
num-	Product	product	change	cific	B.t.u.
ber		per hour		heat'	per hour
		Lb.	° F.
13	Milk	20,000	109.5-161.5 1.0	1,040,000
29	Milk	20,241	87-104	1.0	344,097
24, 25	Milk	5,160	70-190	1.0	619,200
71	Whey	20,000	110-195	1.0	1,700,000
72	Whey cone.	17,000		J	5,900,000
127	Water	25,000	60-120	1.0	1,500,000

Total B.t.u. per hour required _ 11,103,297

' The actual specific heat of milk products is less than 1.0, but for simplicity, a value of 1.0 is used in these calculations.

' B.t.u. per hour requirements based on recommenda- tion of manufacturer.

The estimated requirement for heating the building is based on 10 B.t.u. per hour per cubic foot. All areas of the building would be heated except the hallway, which is a principal exhaust area ; the boiler room and whey-processing area, which are heated by radiation and motor heat; and refrigerated storage areas.

The areas to be heated follow :

Cu. ft.

Laboratories, offices, office restrooms 29,770

Paraffining and hoop-washing room 35,104

Restrooms, lunchroom, and lockers 24,784

Cheese processing, pasteurizing room 210,560

Dry storage, cheese storage room 25,600

Repair shop 8,000

Whey storage 6,144

Receiving shelter 25,600

Total area 365,562

B.t.u. required (area X 10) = 3,655,620 The computed requirements for heating the products and the plant are 14,758,917 B.t.u. When 10 percent is added for line and radiation

losses, the maximum hourly B.t.u. requirement is 16,234,808.

One boiler horsepower is equivalent to the heat required to evaporate 34.5 pounds of water in 1 hour, or a heat requirement of 33,524 B.t.u. per hour. Since makeup water is below 212° F., a common practice is to use 35,000 B.t.u. per hour when converting to horsepower.

16,234,808

— — =r 464 boiler horsepower

Two boilers, one 250 hp. and one 300 hp., are suggested for the plant. These units may be operated at 50 percent overload continuously, or 100 percent overload for short periods. This pro- vides for momentary extra steam requirements not included in the above calculations, such as for the hoop washer (49), conveyor pan washer (48), paraffin tank (57), and laboratory equip- ment.

Ventilating and Air Conditioning

Three types of ventilating and air-condition- ing equipment are used in the suggested plant. They are (a) window and roof exhaust fans with ceiling suspended unit heaters for winter heating, (b) recirculating- type air-conditioning units with provision for heating, cooling, and filtering air, and (c) recirculating-type air- conditioning units with provision for heating, cooling, and high efficiency filtration.

WINDOW AND ROOF EXHAUST FANS (130) WITH UNIT HEATERS

This type of ventilation equipment is sug- gested for the receiving shelter, whey-process- ing room, refrigeration room, and boiler room. Roof-mounted exhaust fans capable of giving one air change every 4 minutes should be lo- cated here, with supplementary roof exhaust fans in the boiler and refrigeration rooms to give an air change every 2 minutes. The supple- mentary fan in the boiler room would be used on hot days to exhaust radiant heat from the boilers and in the refrigeration room to remove the heat from the electric motor and switchgear given off by the electrical distribution panel. In addition, the supplementary fan in the refrig- eration room could be used for rapid ventilation if a serious ammonia leak developed. Both the boiler and refrigeration rooms should have

42

MARKETING RESEARCH REPORT NO. 891, U.S. DEPARTMENT OF AGRICULTURE

large window areas with insect-proof screens on the outside walls.

The repair shop should be equipped with a wall-type reversible exhaust fan, which can be operated in either direction, according to the personal preference of the workers.

The whey-processing room would have its ex- haust fan located over the evaporator to elimi- nate as much heat as possible given off this unit.

The unit heaters would be used for winter comfort. They utilize steam from the boiler, condensed in a finned coil by an air-circulating fan. The unit heaters are temperature-con- trolled by room thermostats, with manual start and stop of the fans.

RECIRCULATING AIR-CONDITIONING UNITS FOR HEATING, COOLING, AND PURIFYING AIR

These units are located on the roof, with dis- tribution ductwork on the roof for most areas. Thus, no dust-catching ductwork is located on the ceilings of the cheese-processing areas. Since the office and laboratory areas have sus- pended ceilings (10-foot ceiling height), distri- bution ducts are located in the space between the structural ceiling and the false ceiling.

The purposes of these units are to (a) con- trol air purity, thereby improving product qual- ity by reducing the opportunity for any bacte- riological contamination or bacteriophage at- tack; (b) control air temperature for worker comfort; and (c) control humidity with reason- able ranges so as to prevent condensation of moisture on the walls, ceilings, and equipment, and to add to the comfort of the workers.

Air-conditioning units of this type are sug- gested for the starter room, locker room, cheese-processing room, and reception room.

Air is returned to these units via ducts lo- cated near the floor so as to pick up moisture- laden air at the low level. The units are equipped with fresh air inlets and automatic dampers to control the ratio of fresh to circu- lated air. In winter these dampers automatically adjust themselves to deliver 45° F. air to the heating coil. Thus, when the outside air is 45° or above, all fresh air enters the plant. These dampers are controlled by a thermostat in the air-stream discharge from the dampers.

From the mixing chamber, the air passes through filter elements which remove airborne dust particles. Aside from good housekeeping, control of dust is most important in eliminating poor cheese sets, contaminated cultures, and bacteriophage.

Next, the air passes over a cooling coil refrig- erated by 38° F. chilled water, which is circu- lated by pump through the coils. The air is next brought in contact with a steam-heated coil for winter heating. The heating and cooling coils are controlled by thermostats in the room. For heating, a constant discharge temperature is maintained by a bypass around the heating coil, which is controlled by a damper so as to main- tain a set temperature after the heated air and bypassed air are blended together. The cooling coil is controlled by a room thermostat which starts and stops the water circulating pump, plus arranging the fresh air inlet dampers for 10-percent makeup air. Units 124 and 124A have solenoid valves which are controlled by the room thermostats in their respective areas. These units (124 and 124A) are arranged so that the circulating pump (97) is off only when both solenoid valves are closed.

The unit maintains a slight positive pressure in the areas serviced, so that leakage of air is out of rather than into the building. This in- sui-es that air entering the building is filtered.

The circulating fan is two-speed. High speed is used whenever the cooling coil is operating or when stepped-up ventilation is desired during periods of cleanup.

The air-conditioning units maintain a 72° F. temperature in both winter and summer except on extremely hot days. On these days a differ- ential of approximately 15° is maintained of inside to outside temperature.

The air-conditioning and purifying unit (123) used for the culture and mother culture room is similar to the units described above ex- cept that (a) the cooling capacity is such that a 72° F. temperature can be maintained through- out the hot weather, (b) the air passes through a second set of filters which removes 98 percent of airborne bacteria as well as microscopic dust particles, and (c) the fresh air intake is located 30 feet above the roof to minimize the chance of air contamination from a nearby plant.

l&U S. GOVERNMENT PRINTING OFFICE: 1971 O 399-602